I realize this was posted 7 months ago, but i wanted to add that this EXACT same thing happened to me. one minute he's there, next hes gone. I personally think the three cage mates ate him. They were an evil bunch of toads. Mine escaped probably 2 months ago, and I have yet to find a body.
-Dustin
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1.1 Crested Geckos
1.1 Fat tailed gecko
0.0.3 Fire Belly Toads