Two things , Have Pay Pal given a reason ? i.e. is the card used to pay you stolen, or has the Card holder denied the transactions as being correct?. I assume you have the name and address given by the purchaser? Is it local to you ( or anyone that you know well ) so as to enable a visit, be very polite as the occupiers may not know anything as there is the possibility of a 'Mail Re-direct' to another address, also if you E mail me the address I will be able to check if it is a 'Mail Drop'
Have you E mailed the purchaser?