Missing keys

My father has managed to "misplace " his car key - somewhere between the carport and inside the house. Mum and I have searched everywhere but it could be anywhere and we have our suspicions that it might have been thrown out. It will cost $400 to get a new one. My father doesn't have a very good track record with keys - he once posted keys home from the UK to Australia that belonged to a campervan we were selling in the UK before we left to come home