Definitely the first thing I thought was "I'd hate to leave my phone unattended with perfect strangers".

Being hustlers I am sure they could have sourced a gym locker rack from a out of business gym for free or cheap. Which would be a bit better.

They have displayed a weak grindset

Well it could be interesting then, to see what happens to your phone and get knowledge as a security researcher.

Reminds me of the Evil Maid attack as pictured in https://objective-see.org/products/dnd.html