Beware of buying "demo" sights - Sightmark Sure Shot Reflex Sight

I bought this sight labeled as a "DEMO" for $20. I couldn't pass up that deal so I got it. shipping was quick, and it was in mint condition when it arrived. After a few months of sitting in it's box with ZERO use or mounting because of this rona mess closing all the ranges, once they reopened I tried it out on a 9mm Scorpion Evo......The lens of the optic fell out after the first shot. I looked at the edge of the lens and the interior of the frame and saw there was barely any glue residue if any at all. When I was purchasing this product it specifically said that "DEMO" products were opened, but UNUSED, and only used for display purposes. It never said anything about them being completely broken or unusable. This is why I gave the DEMO version 1 star. I still recommend Sight Mark products because I have another model that I have used for years with zero issues and know it's a good quality brand. I cannot return or replace this on Optics Planet because the 30 day return police is long gone (I couldn't use it until ranges reopened), but I will try to contact Sight Mark support and see if they can do anything about it. Worst case I can find some kind of glue or sealant to get that lens back in there and keep it there, at the cost of my own dime...