Returned item unable to forward

[bootsiesattic]

I shipped an item to the winning auction bidder on Oct. 2.  The item was returned today with a sticker stating RETURN TO SENDER UNABLE TO FORWARD, among other things.  When I looked up the buyer's information, a different address was there.  I sent the buyer a message asking if it were the correct address.  I'm wondering if I should wait for a reply no matter how long it takes, or just ship the item, chancing that the information is correct.   Also, when I ship the item, should I include a copy of the RETURN TO SENDER message?