These are the days of sheriff and police departments having drones for areal observation.
I suggest everyone put a unique series of large numbers and or letters on the roof of your trailer to help in it's recovery.
I had some left over 14 in tall black vinyl 7's and 0's from my last race car build. So I put the number 7700 on the roof. The trailer was white.
If you want to make if even more visible at night, use IR reflective vinyl.
I lived in the LA area and if my trailer ever got stolen, I figured a white trailer with 7700 in tall black letters on the roof would stand out like a sore thumb from the air by either a traffic copter or a UAV in LA traffic.
Of course the stupid thieves will not even know the number is up there.
Just a thought.....