They don't like to be misted when they're babies. Don't worry and keep misting him.
My dripper runs all day long but I see my 4 month old veiled drinking mostly in the morning right after I fill it.
How fast is the drip? It needs to move 2 or 3 drops per second for them to realize there is moving water there.
How accessible is the drip? Does he have a branch alongside of it where he can easily get to the water?
He is probably drinking when you don't see him, they can be shy about things like this, especially when they're young.
I think you need to have it drip for longer periods than 1 hour.
-Brad