Is this for real? can you post the transaction proof that you made a transaction to that person. Just like others said please be careful on who you are dealing with. 'coz anyone can scam you as easy like 1,2,3, they can risk there accounts on BITCOINTALK just to scam people. Others buy some higher rank accounts just to scam a person. So next time please be careful on who you were dealing with.
Do you mean the PM to agree with the transatction or the PP screen image?
all the evidence that can link to the scammer, you will need to audit all your conversation. In order to have a concrete evidence to the scammer. and if that account is a high rank in this community. Neg trust will be the best solution for the payback time. But i think the scammer will keep your money and won't return the money scammed from you.