Is he scared of storms??
Were there storms(even without rain) the day he went missing???? Maybe he took off scared & hid in a rabbit hole trying to hide from the storm? I know the weather has been freaky this year & maybe he senced it & it freaked him out?

Does he react to the sound of kibble hitting his dish?? maybe walk outside with his dish & a handful of kibble, scooping it up & dropping it into his dish. You might hear him bark or cry if hes stuck..

Heres another idea!
Do you know lots of kids? Maybe offer them a couple hundred dollars if they help you sweep the woods.. if they have dogs tell them to bring their dogs to help find your little pooch.. not to sound down or anything, but let them know its ok if they find him passed away, you'll still pay them.. as that'll make them look really hard knowing they'll get money regardless! <-- I hope that doesn't sound too negitive, but atleast you'll have peace of mind knowing hes not lost & you can properly greve if he has passed

I really do hope for the best & wish you the very best!
I don't know the heartach of a missing furbaby, but I've witnessed it & I'm giving you internet *hugs* to help comfort you & best wishes