most unlikely place to find an animation cel

You know the most sought after thing about finding an unseen peice of physical media is the places you find them.
Like the time a couple of the Sailormoon Toon Makers animation cels were found in a storage locker of an animator.

so, my question is,
what would be the most unlikely place to find a rare animation cel?
Like Sonic OVA or an unused scene from a show

In 2004, 250 Disney pieces of original animation art, which were handpicked by Walt Disney himself, and included many key cel setups mostly from Sleeping Beauty were found in a janitor's closet in Japan at Chiba University.

https://www.nytimes.com/2008/03/18/arts/design/18anim.html

Now that, is random :)