I like the electric fence, except I would forget it is on.
Again, moving is not an option, since I have a good rate and storage is hard to come by (I am in the LA area) and all storage yards experience this type of thing no matter where. I find it fascinating that there would be a suggestion to move the trailer 2 hours away to avoid this situation. That strikes me as quite unrealistic and I'd be suprised if anyone actually does that?
I plan to harden the storage in some nominal way, because my assessment is that the losers that are stealing are unmotivated (why did they not crowbar their way into the trailer itself this time?) and so they will be easily defeated by even the slightest upgrade in security. It will be they who shrug their shoulders and accept defeat, not me.
PS I will most likely end up keeping my griddle at home from now on, or in my more secure compartment. That is a better plan than driving 2 hours each way just to grab my trailer for a weekend run that itself is 2 hours away.