At least here the police also investigates suspicious stuff...not just for criminal action. they could find out by his adress if he's alright?
Best idea imo now is that someone with his adress pays a visit if its not too far, and if he's not there leave a note or ask neighbours if they know anything about his leave.
I called him on skype, on his mobile, emailed him, pmmed him on 2 different places.
Il ask dave for his adress to send him a letter as well....although i do not have high hopes anymore.