Russian Tortoise lost outside, help!

We've had our russian tortoise for 6 months. Since its been nice out we take him outside. All he did was burrow and we kept a close eye on him. Well 2 days ago we were distracted with the kids and forgot to watch his progress. Now we can't find him. We put him in the dirt in front of our house,the bricks are two high except for a couple spots where we haven't finished. So we don't know if he burrowed deep. Or if he wondered out that spot. We've looked under every bush and tree. I'm afraid he's cold at night. Is he wondering where we are and why we haven't gotten him and brought him inside? We're panicked and feel sick with worry. Can he survive? Where should we look?