I'm sorry that your bag was stolen, but did you not lose the key you were given in the first place? I know that losing such things happen to the best of us and you have suffered some severe consequences as a result. I hope it works out for you.

As a suggestion for the future, I always had an elasticated key ring that I could slip on my wrist in order to avoid any similar problems.

However, as to insisting the staff produce a duplicate key because "you're in a hurry to leave" - well, maybe they don't keep the duplicate keys (if they have such) in a readily accessible location to try and prevent any thefts. Also it is standard operating procedure to get a key fee if the one given out is lost (it has to be duplicated or the lock replaced and this costs time, effort, and money - nor can the locker be used in the meantime).

Signature line > "You can't fix stupid"