So long as item bought and paid for then contact details need to be exchanged, how else do ebay think you can complete the sale?
Do you have your collection item showing in ITEMS PAID AWAITING DISPATCH, if so clicking on details of payment should show buyers address and phone number. You could therefore use phone if other means not possible.
You may not see the details, I have never sold a collection item, so do not know exactly how you are advised that payment has been made.