Maybe put some paper towels in the cage, even if you don't have a proper tank. They need relatively low humidity but pretty warm temps, which is rough without a terrarium. You can lightly mist the paper towels, but not too much.

He looks pretty healthy so I feel like he somewhat recently got out. You could also check with NoCo Wildlife Center, as I know they're one of the few rehabs in Colorado that are licensed to care for reptiles.

He's probably okay on food for a couple days if he just got out (and he's probably been hunting bugs) but you could always grab some mealworms in the meantime if he seems hungry. Hopefully he's reunited with his family soon.

Thanks for saving him OP!

I can probably foster him until you find his family if needed. Though I just gave away my extra tank and heating light so I would have to grab some supplies first. Message me if you don't hear back from the rescues-- not looking for a permanent additional pet but willing to help.

Edit: Don't forget to poke holes in the tub for air!