I bought a 10 dollar ceramic log the ACF I'm currently keeping in a 10 gallon until he's large enough to not get eaten by the large ACF I keep.

He prefers to hide behind the Whisper 10i filter I keep in the tank and never uses the log. I think when they're young frogs they just like to jam themselves behind objects to feel secure.

I wouldn't worry about it, he'll get too large to fit behind the filter eventually. All my frogs did this when they were small.