WatchaMeanThey if you go to the Store on your console and look for it there, if you've bought it it should say that it's owned and let you download it again. You can also check your purchase history here:
https://support.xbox.com/en-GB/help/subscriptions-billing/billing-payment-updates/check-xbox-purchase-history
If you're still having problems, there's an option there to speak to Xbox Support. They're the people to speak to about purchasing problems on Xbox. I'd recommend Live Chat, they usually don't keep you waiting too long and I've found them helpful.
