Have you tried playing hardball with the liquidaters? They cant sell the boat (you own it) so what are they going to do? Keep paying customs for storage fees? The liquidaters are now liable for all costs incurred by the bankrupt company from the date they took over (new costs).
If you paid for shipping via credit card have you tried using inbuilt fraud function and claim the shipping payment back?
End of the day I cant see how anyone can do anything with your trailer if you havent signed anything saying they can. Just make sure you keep lodgeing the required forms with the liquidater. I imagine once the company is liquidated completly and closed the shipper/customs will have to release the items to you, in the mean time they try to use them as a way to get paid.