Did that too, it's a pretty bare tank with just one piece of driftwood and one cave, but it's super easy to see inside the whole thing, and he's not there either.
Had the day off today, took everything apart again, both filters, all tubes, all decorations, sifted through every inch of sand with my fingers and Nada. I know he's gotta be in there based on the smell and his disappearance, but I'm out of ideas
Is it possible he got stuck up in the tank lid or light? Depending on how high the water level is I can see this being a possibility.
Only other thought is a hollow ornament or the cave that he got stuck way up inside. Or, a hole or crease in the driftwood that he was barely able to fit up into.
Only other option would be in the substrate somewhere. Maybe he got way down into a corner or edge somewhere.
Hope you can figure it out without having to break the whole tank down.
Here's a pic of the tank so you can see what I mean, pretty bare, not much he can hide in, solid wood all the way to the ground, and surrounded by hardwood floors, no where to hide