Help! Boosters have gone!

Hi @KJP650 and welcome to our bubbly community. 
As @kaiser1618 correctly told you, they are saved within the game memory so if the game is reinstalled, they do go. King cannot replace saved boosters, but if they were ones bought with real money they can replace those. 
Have a look in the community though starting here and you have a chance to win

Unfortunately yes, but King don't recommend that you store a lot for this reason. As often sometimes the device itself can cause issues and reinstall it.