Being glass was it broken? I regularly have breakages that no one admits to, and guests usually think that it doesn’t matter as they have paid for it by staying.
At the last air bnb I stayed at I took home a tea towel! Didn’t mean to, must have shoved it into a bag when packing our stuff from the kitchen. Probably not out of the scope of possibility that a small throw rug could end up in shoved into a badly packed suitcase. Though if i found something more valuable than a tea towel accidentally in my bag I’d let the host know.