Cant' find homeowners, what to do?

I’m in the process of buying a house through a short sale with the bank. They sent me the paperwork for the homeowners to fill out. The owners are out of the house and have been for several months. They moved out of state. Calling old places of work, or cell number doesn’t get results.
Any suggestions on how to track them down?
Do I need them to do the paperwork?
Will the bank move forward with a shortsale without the homeowners hardship letter?

Thanks all, and yes I’m new to this.

SS specialists will probably chime-in but the reason you’re having trouble finding them is probably the same reason you got the property, they’re hiding from the bank.

Use a skiptracer. You’ll get names and addresses of them, their family, their neighbors, everyone they ever did business with, and a bunch more stuff. It’ll cost between $10-25.

You can also mail to their old address with “Return Requested” on the postcard to see if the post office knows where they’re at.