Ok, look, I know what the laws say, and that's all fine and dandy, but no one seems to have the best interests of the frog in their head.
It's probably not eating because it's suddenly been taken from the wild, a place that it knows and has done all its life, and has suddenly been thrown into a cramped (compared to freedom), confined space where it can't get out.
I'm not trying to sound callous, but Miss B, when you said something along the lines of "Let it go? But why? It's not illegal.", or whatever was said, it made you sound selfish and uncaring.
Why not let it go? Set up a pond in your backyard, and attract frogs, but don't try to keep them confined. It's not natural to them, and it's been known to stress and (if it's severe enough) kill them. Doesn't that sound cruel to you?
I have absolutely nothing against you, and certainly nothing against owning frogs (Even I want some, eventually), but captive-bred frogs, not wild ones. You could buy some frogs, ones that have lived their entire lives in an enclosure, and enjoy them.
Whether someone has a licence or not is irrelavant, people shouldn't take native animals from their yards and try to keep them. And (I'm not saying you're not able to) sometimes people don't even know how to look after them correctly, and end up killing them.
Laws or not, it shouldn't be done.