Doesn't Paypal issue the seller an eCheque when the buyer has an attached bank account but no linked credit card? Because it takes a few days to finalise a bank transfer, the eCheque clears when the transfer is completed, but if the account has insufficient funds and no overdraft facility, the eCheque will bounce.

It sounds to me like the OP's bank account debit card probably does have an overdraft facility as many do these days, so the eCheque should clear in a few days as per normal.