Have you got any mutual friends who would know where he was (or a partner or family) or have a new contact number?
You could try the phonebook for a landline number.
If his phone isn't working, have you tried e.mailing him or messaging him on Facebook. I'd put your number as well in case he has had a phone lost or stolen and doesn't have it anymore. I've lost my numbers a few times through that.
If he was made redundant, could be he has had to change phone/provider, internet etc...