Mouse within the house problem!! Think its stuck, will it smell? My cat recently fixed to bring home a mouse, problem is...

My cat recently fixed to bring home a mouse, problem is he doesn't play with it til its deceased, that I can just more or less handle, no he brings it surrounded by alive and then runs out the cat flap and no longer interested!
So very soon I have a mouse surrounded by my kitchen, not happy as its be through all my cupboards and nibble on most of my food packets. Tried catching it next to a humane trap, didn't work, my friend tried trapping it where it be sleeping so she could catch it but it manage to run up the back of the gas boiler. Since later I've not seen it, not sure if I've hear it in the dark or if I'm now over sensitive to any roar. Could it have get stuck or hurt behind the boiler? If it have been hurt and died will it start to smell and result in more problems?!

Last night I put some chocolate out to see if it go so I know the situ, but its still there this morning.

Not used or cooked surrounded by my kitchen since last week when clean visitor arrived, too paranoid more or less germs.
Please help, any guidance is great!
Answers:    Yes - if it's dies it'll lay there rotting and you'll obtain a vile smell for two or three weeks. Think of me - I had a squirrel come contained by and get stuck somewhere at the back the skirting (but only after it have shredded some of my fitted carpets whilst trying to tunnel its route out)! Stank the place out for a month - and we never found the damned thing no issue how hard we tried ! ! !
It'll smell for a while as it decay but once it's just a skeleton you won't know it's here. Also depends on if the area it's within is dry or not. If it's damp later you're gonna be buying air freshener for a bit longer.