I'm confused.
what did he do at the bottom of the cage?
well anyway 5 inches isn't really enough, try and get as much in there as possible.. the more the better.
and most scorpions aren't very active, they seldom leave thier burrows apart from sometimes during the night. whenever they do it you aren't likely to see it.
either way, a scorp that stays in it's burrow alot is a happy scorp. And you don't need the black light.