What are some examples of lost media being found at stores?

Not a store but I know a special called Izzys Quest For Olympic Gold was found on a home recording while a guy was cleaning his garage.

There's a used manga/anime/Japanese pop culture store in Vancouver Canada filled to the brim with stuff, including CDs and VHS tapes, several of which look like home recordings. I would not be surprised if there's something hiding in there.

where is that?

Yep. It's called Halfmoon Bookstore.

It is legit. Here is the link for proof: archive.org/details/spongebob-nastypatty-workprint 

here's the correct link: archive.org/details/spongebob-nastypatty-workprint