If you cannot relocate the clown, you might consider relocating the coral. Really depends on what light you have over the refugium and what else is in it. If nothing else, at least until the clown is caught so the coral does not receive further injury. You should also be aware that if the clown has adopted this coral, there is a good chance it will choose a different one once the frogspawn has been removed.
It is usually much easier to catch fish after lights out when they are unaware or "doppy". If you wait a few hours after lights out and the room has been dark (or in very low light) a while, try again then. They are usually a snap to catch under those circumstances.
Cheers
Steve