Why are you taking the frog to PetSmart? The people that work there know next to nothing about the animals and following petstore employee advice has lead to a lot of sick frogs on this forum. Plus the trip will really stress the frog for no reason.
Also, like I said, just go ahead and replace the substrate with eco-earth. When you said you'd gotten all the moss you could see out, I wasn't expecting pieces that large to still be in there. Like Lija said, just shedding will cause him to eat pieces of it.