You bought coins for USD 3000, and don't remember anything about this guy (e.g. IRC channel or nick or LR account number) or have any record of the transaction? Doesn't sound very likely to me. Are there more suspicious transactions involved?
I was trading in IRC only one time, there is no more suspicious transations involved. As I said before, it was more than month ago, so I can't remember details.
Did you just visit IRC channels at random this one time, and then some random person came from nowhere and asked if you were interested in trading LRUSD for bitcoins? I find this
very hard to believe. Most people at least have an idea what IRC channels they are visiting. Are you afraid there may be logs? Do you remember which nick you may have used on IRC? This story needs a lot more flesh to be even remotely plausible. You may not be the scammer yourself, but you are certainly not helping to find the person. Trying to protect the identity of the scammer, assuming it isn't you, will not get you anywhere.