Man that sux!!! I would be heated! I hate people like that, I probably would have knocked his *** out. Just wait for them to call you back and say it not running and tell them to bring it over and be like
"Oh S*** you really tore this thing to S*** man, Its gonna cost about $3-400 for a motor rebuild" then tell him "I will give you $25 for it as is because I think I can use a few of the parts."
By the way you describe these people they would probably sell it to you. Then after you get it running tell them you fixed it with some other parts you had.
As far as the one on ebay being the same. I dont think so the one on ebay has a pull start and the one he got running he had to push down a hill to get started. Just an observation why push it down a hill if the pull start was working on it?