lairdpopkin

It's hard to say how or why the tag got into their bag. It could have just come loose from another bag and fallen into their bag.

And there was no reason for them to cut their vacation short - that seems needlessly paranoid. The tag did its job and beeped because it wasn't near its owner, and they found the tag and could simply throw it away and the owner of the tag would have no idea where they went after that. 

And if they wanted to see whose tag it was, they could scan it using NFC, which is built into most modern iPhones and Android phones, and it'll give you a link to see the owner's info so they could contact them, etc. https://www.applegazette.com/news/how-to-use-airtag-with-android/