My turtle has disappeared off the face of the earth. ?

I left my box turtle on my patio with the door to inside cracked while I went to cl for two hours this evening. I let the turtle wander my apartment regularly. When I got home he was gone. I tore apart my entire, very small apartment looking. I live on the third floor so a dog or cat couldn't have gotten him. He's much too large to be carried by a possum or raccoon and it was too early for one of them to be out anyway. There is no possible way he could have fallen off the patio. It has 3 foot tall solid stucco walls with nothing close to them to climb on. No one has keys to my apartment except the maintenance and I have no idea why they would steal a turtle. I have no idea what POSSIBLY could have happened to him. Please someone have a good idea! I have been looking for three hours.