They will have to show the returned mail was addressed to that most current address they had for you. If it is addressed to you at that address and was returned by the Post Office for something like 'not claimed' (and the PO would show dates of attempts) then there isn't a lot that you can do about it. The problem may be that the notification from the PO that you had a letter you need to sign for, could have been placed in someone else's box if you never saw it, but they would have had to do that 2 or 3 times.
As far as the creditor, if the above is accurate, then they've fullfilled their obligations to notify you. If they in fact did NOT address and send it to the address on file, then you have a valid argument to make them eat their loss.
Chapter 7 Discharged & Closed Jan 2020
