Car purchased under a power of attorney, under arrest

Hello. Here is the situation: in 2012, the car was purchased under a general power of attorney, and the fact of the transfer of money is confirmed by a receipt that is not notarized. Six months later, the car was seized — the seller acted as a guarantor for a loan that has not been repaid to this day. I plan to file a lawsuit. What claims are best to make so as not to lose either the money or the car?