For all we know, Butters did nothing wrong. Perhaps Butters was having some sort of problem that can not be explained at the immediate time; not trying to spark up any debate, but just pointing it out. Also the $17 that Devilstar2k2 did not receive seems to be the PayPal fees from the money he sent if my calculations are correct.
If Butters intended to steal Shawn's money, why would it still be in his PayPal account 2-4 weeks later?