Would not pictures of the gun with serial number not work for proof of ownership?
In the case of a Glock or a like handgun, the box with serial number on it work to show proof of ownership?
A picture would be proof of former possession. Not sure that would be sufficient for loony Bloomington.
I'd agree that if you still had a serial numbered box for the recovered firearm, that would be pretty strong evidence, but that assumes you had a box to begin with and that it wasn't stolen with the firearm in question.