Yellow Letter "Return to Sender"

[Adrian Smude]

I've been sending out hand written yellow letters from my driving for dollars and just had my first few come back.  Two reasons:  "Return to sender vacant unable to forward" and"Return to sender not deliverable as addressed unable to forward"  

I mail to both the mailing address and the physical address.  My question is there somewhere I can find an updated address or are these dead leads besides leaving a door hanger?