I once lost a model R/C aircraft, someone found it and I got to hear about it through a 3rd party. I contacted the finder and he denied all knowledge. I reported it to the police and the 3rd party acted as a witness. The finder ended up in court and ended up paying a fine, costs and compensation to me, he also earned himself a criminal record. The police informed me that if he had reported the find and I had not turned up inside 6 months the aircraft would have become legally his. If I was you I would return to the police or even speak to citizens advice bureau. - good luck.