They could report there account was stolen and say what recent purchases they had made for proof.
But nowadays there is so much security behind the lines you'll be fine.
Nothing you can do until maybe something eventually comes up. I 100% think you are safe to be honest. I went to the bank yesterday and didn't have my ID on me and they asked for recent purchases, social security, and secert question answer.
Now paypal probably doesnt work like my bank does, but when you play around with someones real money, it isn't that simple.