Were the caravans security tagged? Horse trailers have a security tag on the coupling. Any trailer showing signs of this being removed or missing is viewed as suspecious and would not be touched by a genuine buyer. This will make them very difficult to sell on.

Post code letters and numbers can be purchased. These are around 2ft high and even if they are removed they leave an imprint of the letter/number behind still visable. Not pretty but effective.

Sympathy and good luck in getting your possessions back to all concerned.