You are correct in that the agent should have been working harder for his client the seller
A letter of offer is a nothing, not enforceable and in this case appears to be a waste of time but the agent will probably stop working until it is verified or turned into a contract.
I may have the wrong impression here but I gather that the buyer owned two houses which he had to sell in order to purchase your mates house?
Are there two agents involved or one? Potential conflict of interest if he is working for the buyer and a seller
There can always be a contract written with a subject to clause which states that the owner still has the right to sell even though he has accepted the offer and if he sells prior to the first purchaser being in a position to buy the first contract is null and void
