I'm not a lawyer, and don't really think that the police will be arriving at the OP's hotel anytime soon. However, simply looking at the definition of theft provided by that not-always-infallible website Wikipedia:

"Theft is the taking of another person's property without that person's permission or consent...": The OP has done this

".....with the intent to deprive the rightful owner of it." As I said, the original intent wasn't to deprive the rightful owner of the bag, but it is now. In Wikipedia's definition it doesn't talk about permanently depriving someone of their property - does that mean if I come round to your house and borrow your car for a week because mine is being repaired that it wouldn't fall into the category of theft?