From how I see it, the First Sale Doctrine stops you from reproducing the design and printing your own version of the fabric (and probably product using the fabric design as well) to sell, but does not impose any restriction on you reselling the now second-hand fabric however and wherever you choose (the copyright does not restrict reselling, licensing is what does that). So the apple fabric, being unlicensed, is up for reselling wherever you want as far as I can tell (like the salon shampoo example in one of the links above), but isn't necessarily available for you to use in your own commercial product.
If you had substantially altered it, then you could argue that it has become a part of your original art (which isn't so, because you have simple sewn the material, unchanged, into a bag).
I can't see that you are covered or protected against a copyright claim. But, is that claim likely? And even if it is (it's possible - generic doesn't mean the owner won't find the image online), would they persue it (is it worth it to them?) and could you defend against it (another near identical apple fabric would give a potential defense). I don't know. I might think twice if you are advertising your product with a copy of the bag (and it's image) online.