There has been some very good advice so far. I was worried about the same thing afew weeks ago. Malcolm is on cocofiber. When I cleaned his tank out reciently, I found some turds I didn't see. Often they are big enough to see, so I guess the smaller means he is doing all that much better.

Maybe if you get a glove and carefully skin through your Pacman Frog's substrate, you may find evidence that he is not impacted. As pyxieBob mentioned earlier, checking for a lump near the middle of their belly is also a good way to find out if your Pacman Frog is impacted.

Hope your Pacman Frog is not impacted!