"Well, I have! The first night camping out on the Wonderland Trail, I was awakened by chewing noises. I had my pack in the vestibule, and even though all the smellies were in the bear bag on the pole, a curious mouse was gnawing on the mesh outer pockets on my SMD Traveler."
He was probably after the salt, or what he thought was salt. Porcupines chew on tires in parking lots for the same reason, even though there is no human deposited salt involved. The mesh material may well have had a similar effect on him. That was one of my first learn-the-hard-way experiences, and it cost me a tire. Beyond that, the location says it all. The Wonderland Trail sees a lot of traffic and therefore has a lot of agressive, habituated critters. That is one of the reasons I never hike in such areas. If that kind of area is where you find yourself, clearly extra measures are called for, first off being to bring your gear into the main compartment of your tent. Rodents, especially habituated ones, can be a real PITA, and I quit hiking in areas where they are a problem long ago. They are relentless and it is just too much of a hassle, for me anyway.