There's not many places he could've gone. The gate at the far end looks locked and the fence is lined with barbed wire. He could be in the old blue camaro, poorly drawn old vette, dodge daytona, mustang fastback, that green thing at the back of the lot or the box truck. What do you want to look in first?
if I were an evil scientist, i would be curious what i could rig out of the back of an old spring co. truck. and if i were a guy who wandered into an abandoned warehouse through a mysterious green door and had an incedble advententure, i'd look at the wall behind me and see if there were a ladder going farther up. look up, back of truck, behind the red ride. in that order.
Sounds like you have a good plan. First, you turn around and see no means to escape. Then, you slowly make your way over to the box truck, scanning the fench for holes as you go. You reach the back of the truck and didn't see any holes, so you motion to the prisoner to sneek around the front of the truck and stand by the other back door. With the hook of the crowbar, you pull one of the back doors open and step back in case something comes flying at you. Hmmm, nothing came flying out. It's now time to take a peek inside. Let's see what's in there.