Try posting to FB as well if you haven't yet. Hopefully if the owners are just as diligent as you are in returning him or her back home, you two will cross paths.

Additionally, if you have the time for this (and if I'm not mistaken), if the cat has a microchip, you should be able to bring kitty to a vet office to confirm if chipped or not. Just an option for a last resort measure. Not sure how many owners actually chip their cats, for you may be better off using flyers and/or the internet to locate the owner.

EDIT: Nvm. You said you were gonna see if it's chipped. Good looks.