Originally Posted by gr2020

The 1st of each month, they add the $15 Amex credit to your Uber Cash balance. It will be used first, usually, which sounds like exactly what happened in this case, as expected. It's not a statement credit - it's just added to your uber cash balance, and will expire if you don't use it by the end of the month.

If you go to your wallet, you'll see your uber cash balance at the top - if you tap on that, it will show you the breakdown of the funds you have there, and part of it will show the Amex credit balance, if you have any. So on the 1st of next month, if you go there and look, you should see the Amex credit there.