Did you put "bitcoin" as what the transaction was for? I put "other" as most of my transactions (no matter what they are) and have never had them ask any questions about it.
I used "other" and wrote something like this "Here's the payment for trade ID xxx at BCM"
If they refund the money, I'll get them to djex another way...and I probably wont use paypal again...
This never happened before though...