"Archeologist are still finding clothes made out of natural fabric from hundreds and thousands of years ago."
Terry, It seems to me that you are making the point that natural fabrics don't break down, and using the very small number of fabric scraps recovered at archaeological sites as evidence. That would be silly, though. I must be misunderstanding your point. Very old scraps of fabric only survive under extreme circumstances (in anoxic mud, dessiccated tombs, under perpetually frozen snowpacks, etc.) If your point were accurate, those fabric scraps wouldn't be so precious to archaeologists, and we wouldn't hear about it in the news. Prehistoric fabrics would be for sale in thrift stores. The fact that they only survive under very rare conditions illustrates how readily natural fabrics break down. Put a cotton shirt in a compost pile and it will be in tatters after a year and gone in two.
I agree with the observation that metal hardware may not necessarily be environmentally inocuous due to the byproducts and energy requirement of manufacturing them. But the OP specified that he's only attempting a pack made of materials that don't contain petroleum products. Most fabric dyes are petroleum based, so he'd have to use undyed (or naturally dyed) fabric, but otherwise he seems to be on the right track.
Recyclable would be another endeavor alltogether. And inventing a pack that has the smallest possible "carbon footprint" would be a third completely different undertaking. One could also try to make a fair trade/ethical pack, or a pack with materials made locally. But these would be different projects. The OP explained what he's attempting. An imaginary pack would be the only way to accomplish all of these goals at once.