I can't say why Nanner's refused his meal, but I can suggest that you leave him be for a week or so before trying again. It could very well be that he just wasn't hugry. Maybe enough of his last meal is still in his system that he doesn't feel the need to expend the energy it takes to eat. Or you may be surprised to see his eyes cloud over tomorrow. That happened twice with my gopher.

I know it's easier said than done, but TRY not to worry too much about it. Give him a week and then try to feed him as you normally do. To answer your other question, I do think you'd be safe leaving the mouse in his tank overnight...but I wouldn't refreeze it or anything after that...I'd just flush it.