If you had previously purchased some item from the store and it’s not showing up in your inventory for some reason, the button "Restore Purchases" lets you get that item back without having to re-purchase it. You can find this button in the Game Options under Preferences (see screenshot below).

Please note that this button only restores the following items:

However, Coins Packs and League Packs cannot be restored using this button.

If you haven’t received a purchase made more than 24 hours ago or if you haven’t been able to restore your purchase using the restore purchases button, check out this FAQ here.