If the seller cashed it, I think you will just 
get a copy of the MO with the signature on it.  
No refund will come to you.  If it isn't cashed 
yet, they will refund you the money, but when the 
seller decideds to cash it, the USPS will send 
you a statement saying you owe them that amount 
now.  Its kinda screwy.  I had that happen to me 
before.