But is moving a blanket from one cabin to another really theft from the airline?
Am I a shoplifter if I try an item of clothing on, and leave it in the fitting room instead of returning it to the rack? I think not. Even if I leave it in a heap on the floor of the fitting room. Yes, I'm inconveniencing the staff and effectively reducing shelf stock availability for subsequent customers. But theft?
This seems more analogous to the OP's report than any common definition of theft.