Loan

I would need to know some more facts but I would sue the defendant for the amount of the loan. Obviously it would be better if there was some sort of writing such as a promissory note evidencing the debt, but this is not necessarily fatal to your claim. Besides the merits of the case you would also want to look at how likely you are to collect on any judgment. Does the defendant own a house or other real property? Does he a have bank account or other assets? The first step, however, would be an attorney demand letter followed by a law suit if there is no response to the demand letter.