It's not that unusual. I work in the medical device industry and we need to do quite some testing with early prototypes for all sorts of stuff like biocompatibility, cytotoxicity, hemocompatibility as well as pressure tests, drop tests, leakage testing and whatnot. Each and every one of those prototypes is hand made and therefore the "only one".

Even if they pass one test with flying colors and no visible damages, we couldn't use them in another test because they need to be factory new to satisfy regulatory protocols.

Normally we don't ask for those back, we are more interested in the ones that failed a particular test.

Now we wouldn't want our prototypes to be auctioned off, naturally, so the test centers we work with have to ensure they'll be destroyed (we have contracts and NDAs in place). But not wanting a prototype back after a third party played around with it is way more common than you think.