I used to use a hitch receiver lock back in the towable days. A YouTube family we follow had their trailer stolen... even with a lock.
I didn't even purchase any type of lock for our flat tow setup. The Blue Ox tow bar goes in a storage compartment as part of our camp setup routine... out of sight - out of mind.
Hope yours wasn't damaged in any way... it sucks, but there's bottom feeders looking for any opportunity.
Be creative, and have a fun life...
...and don't be an @**hole! -Ken Block