Maybe some aspect of that person's PP account status or of the transaction itself caused PP to reverse the payment. PP probably has security measures in place that send up red flags when certain aspects of a transaction don't match the expected parameters.
Credit card companies do this sort of thing. That's why it's recommended that card holders call the CC company if they'll be using their card during a trip abroad. Otherwise, the company might decline the transactions that occur in the foreign country because they know its not where the card holder lives and suspect the credit card has been stolen.
