One of my kids set some coins on top of the sliding lid/cover of the mobile charging unit. As I drove off, they slid underneath and I have no idea where they went. Concerned they’ve fallen into somewhere in the engine or gear box. Anyone know if that’s possible. 

Unless you have open holes in the top of your gearbox or engine it wouldn't be possible. They'll be rattling around the back of the centre console somewhere!

Theyll just be in the bowels of the dashboard, theres a lot separating the inside of the car from the engine and transmission these days!

Thanks guys, good to know it shouldn’t get into the mechanics. A rattle will really get on my nerves though but no noise so far.