You should seek help from an attorney in your area on the matter but my gut instinct is that you are going to have to sue them or get them to sign something that gives you a judgement against them and allows you to file the judgement as a creditor so that the trustee is aware that there is a debt owed bfore dispensing with the funds.  With out a judgement there can be no lien, as you say.  You can, of course, enter in to a written agreement with them as well that can be submitted to the trustee and the court for approval and then the trustee can honor that.  It is easier as long as they are agreeable to it.  Good luck.