Oh gosh I hope you find him, my rabbits sometimes get out on me too and I have never lost one yet. Then again I live in the middle of nowhere with very few predators, one of my rabbits was gone for 24 hours and another one was gone for (I will probably get slaughtered for this but heigh ho) three days before we finally caught her.
At night they will usually go and hide, I found with my rabbits that got out they would come around their pen or the shed in the morning and not stray much farther then the garden. If he can, he will come back during the day you just have to keep an eye out for him.
Mine were in their element when they got out, when I tried to catch them they binkied away happy as Larry.