My credit has disappeared
Firstly, don't worry. You'll be able to get your credit back. What's probably happened is it's been redeemed as a gift card and you'll be able to see it in the rewards panel.
Firstly, make sure you're logged in to your account.
Click the yellow 'Rewards' button at the bottom of your screen. If you're on desktop it will say 'Rewards,' if you're on mobile, look out for the little present icon.
Click 'Your rewards' and you'll see all the gift cards you've redeemed.
If you'd like to spend your gift card on an order, follow these steps.