I don't know much about trailer security but anyone ever tried one of these?
http://www.trailerlock.com/five.html
Five important facts every trailer owner must know
Trailer coupler locks, (hitch locks, tongue locks) are all very easy to defeat. Thieves attach the "locked" trailer coupler to their tow vehicle with chain or rope and pull the trailer out of sight or they use a special device that just clamps around the locked coupler and hooks directly to their tow vehicle.
Law enforcement officials recommend wheel locks for trailer security.
Trailer theft is a huge problem and it's rapidly getting worse.
To thieves, a trailer means money on wheels -- an easy target asking to be stolen.
Trailer insurance coverage alone is not enough protection. If you leave your trailer unsecured and it?s stolen, you?ve got to pay the deductible, deal with aggravation, down time and inconvenience plus likely increased premium rates and possible cancellation of your policy.
I hope you find your trailer Stu, I'll keep an eye out for it out here along with that Green Jeep that was stolen.