An unrecognised charge may be an authorisation hold, which is never actually charged to your account, but may appear as 'pending'. All authorisation holds are voided within a few business days, depending on your bank's policy. We issue authorisation holds as a way to better protect against fraud that may result from unauthorised card usage.
If you are still unable to recognise an Uber charge on your account, please share some info here. We're happy to review.