We have a pet Wood Turtle (about 5 years old now). He can, at times go a week without food (and water). He mainly lives in a 3' x 4' aquarium (about 90 gallons), but he loves to be let out to wander the house for a few days. He's big enough now (about a 8 inch shell) that he can't fit anywhere were we can't find him. We typically find him sleeping under a couch or some dug into a corner somewhere. A wood turtle is less aquatic than the more common Red Eared Slider, so he seems to enjoy walking all over the house, and he's quite capable of eating when now in water.
I think the turtle will suffer more quickly from a lack of water than of food, but reptile skin is typically very good at holding in moisture. I do notice that my turtle is quite a bit lighter after a few days of being out, compared to when I lift him out of the water.
As your question was asked a long time ago, I do hope you found your turtle. I'd suggest other turtle owners to be confident you can find your turtle before you let him wander around your house, and to look diligently for him if he's been out a few days.
Sorry to hear that but any thing could happened some 1 could of found it and kept it or threw it in to a lake or some. Thing I don't wanna make you up set but it could of died :(
most reptiles can live for weeks without food some even months.
ask missgaga she had a turtle~~~~