Sale of 180 scooter not enveloped

Hi, I have a problem. I sold my 180 scooter on October 3rd 2011 (with season registration from April) and it was stated in the purchase contract that the scooter must be deregistered by the buyer by October 10th. He did not do this and sold the scooter again. I asked him to clarify the matter, but he thought that the scooter automatically unsubscribed after the season and he could not reach the new buyer either because this temporarily in china se I have also described it to my insurance company and sent the purchase contract. They have contacted the licensing authority. But until that happens, something will definitely take time. What can I do for the quick, so that he is not registered again on me from April 1st, is insured and I do not have to reckon with costs. Unfortunately, I have no legal protection. Would be great if someone could give me advice.