I would be seething if someone took gear when told not too, let alone the washing disaster. I would let them buy the sleeping bag at replacement value. My kids were headstrong as teenagers (still are!) and I had to keep my gear separate or things would "migrate" all too easily. I am amazed at the problems some have with boundaries.

There are several possible problems with the bag causing loss of loft. Most have been mentioned already. To recap:
1) Physical damage to the shell
2) Lack of rinsing, leaving detergent or soap in the down
3) Physical damage to baffles from agitation and/or mishandling while wet
4) Incorrect or incomplete drying

I sort-of doubt that a detergent induced removal of embedded oils would be noticable as loss of loft immediatly. This would take some use/compression of the down to break the plumes. Usually the down dust will become noticable as "clumps" in the fill that are very difficult to break apart. Sometimes you may notice just a loss of loft on thicker bags. As you say, it may not meet it's temp rating.

Down is fairly resistant to heat up to boiling temps. Not so, the shell. If the shell is not damaged (zippers, pockets, and hood) this can be ignored. Use low or medium heat with frequent stops for hand shaking while drying. I use my home dryer for this, but, it is extra large capacity. Also several dryer balls. These are about the size of a tennis ball but have "porcupine quills" on them...three or four on my 0F bag, two for my 32F bags. Tennis balls are the standard, though. 4-6 of these work well.

I agree that any soap or detergent left in the bag will cause loss of loft. Try plain water on an extra wash cycle with extra rinse cycle. If the bag is over 5" thick, you may need to do this twice (6 rinses.)

Using down wash will not buy you anything. Adding soap to detergent is probably not a good idea, if there is *any* detergent left in it. If the damage by detergent has been done, there is no feasable way to restore the embedded oils to down. They are part of the structure and, if lost, cannot be replaced. The down will degrade over time, especially after the next use. But, it will be difficult to tell till it is used, or, compressed in a compression bag and shaken out. It just won't reloft. I believe that WM, perhaps others, will add more down if this is the case. Ater drying it thuroughly (as others have said, a longish process) you can return it to them for restuffing. This will add a few ounces, but, you can avoid buying a new bag. Perhaps the person responsible can help pay for it?

Down bags and stuff can certainly be washed OK. But, it takes a very mild soap. The embedded oils are washed out at EVERY washing to some degree. Even plain old water will wash out some. Body oils can stick to the embedded oils in down, also. Generally, anything that cleans body oils out of the down will also remove some of the embedded oils along with it. So, keeping the bag clean vs down degradation from body oils is a problem with down. Down wash is supposedly mild enough to remove this "loose" oil, without removing embedded oils. I often recommend about 1/4 to 1/3 as much down wash as what is recomended on the bottle, though...just enough to clean the bag, but, not enough to deep clean it. What is not cleaned will get washed next time...

If you are really seeking a return of the original loft, you will NOT achieve this with air drying without EXCESSIVE handling, fluffing, you name it..... Find the largest dryer possible - friends large capacity, laundromat extra large capacity, local hotel's commercial dryer.... anything that will tumble it somewhat freely. Be sure to check the dryer first by hand for snags or rough spots and watch the temperature. Tennis balls in a home dryer add amazing loft to a bag.

Thank you everybody for some great advice!!

I ended up putting the bag through about 4 rinse cycles at home. I am going to take it to a laundromat for a dry cycle with the tennis balls.....and a book to wait with :). I'll keep you guys updated.

Just an update.

After the 4 rinse cycles it's been drying outside under cover for days now. I haven't had the chance to take it somewhere to get it dried with tennis balls but I can tell you the loft is MUCH better already!! I tried to squish it down to get it in it's bag but the loft seemed much better and I had to wrestle with it a lot more than usual.

Thank you for the info guys!!

Thanks for the update!

Many years ago a friend asked if her college grad son and his girlfreind could borrow two sleeping bags and mats for a cross country camping trip.

The kids came to my house to pick up the gear and I lent them two inexpensive synthetic tapered bags and two nice CCF pads.

After their trip was over his mother called to say that "You can come over and pick up your gear." To which I replied, "Connie, do you mean to tell me that they are not going to return the gear themselves?" and she said they had already left town.
I told her that SHE would have to bring the gear to me just out of common courtesy.

When she finally brought the gear back I discovered why the her son didn't return it personally. The pads were both torn and the bags had jammed zippers and were filthy.

NEVER LEND GEAR UNLESS YOU ARE GOING ALONG AS WELL!

STOLEN GEAR (your sleeping bag) AUTOMATICALLY BECOMES THEIR PROPERTY AND THEY MUST REIMBURSE YOU FOR THE COST. PERIOD.

Sounds like it will be OK after all...
My suggestion to anyone wanting to use a washing machine for the job is to run a hot cycle without any clothes/detergents before doing so.
That is so some or possibly all of the detergent residue is washed away.

Eric, that's an unfortunate story!

In the end I fixed the problem (thanks to the info from all you guys) and now the person 'may' be buying the bag off me anyway...I'll upgrade if the sale goes ahead. A sale of a WM bag from a person on this forum didn't go through due to PayPal issues but I have my eyes on a Feathered Friends bag that is got better quality fill (covers for colder nights) and weighs less anyway.

Decisions decisions.