You need to be able to save after the shop, or any time. Have a look at the Persist behaviour because it sounds like your problem is with the coin objects and their state. The Persist behaviour added to the coin means they won't reset.
You can in theory save only the global variable in local storage each time and keep loading its value, but why not save the whole game ?
If this still doesn't resolve it, please give a better idea of what the game is and the design around the coins and the resetting.