Originally Posted by ajax

The right and proper thing to do is to contact the hotel and ensure that they have billed you. If their systems say they have, and the charge does not show up on your card, then there is little you can do with regards to the hotel getting their money.

If you have already been reimbursed for these charges by your company, then it is not right for you to keep the money if you are not ultimately charged by the hotel.

I would probably do something like this: tell whomever you need to at your employer that you've been reimbursed in good faith but for some reason not charged. Set the money for the hotel charge aside in your account so that you can access it easily if need be (i.e., do not spend it). Agree with your employer a reasonable amount of time to wait for the charge to show up (e.g., six weeks). If it has not shown up in this time, return the money to your employer, but make sure they know that you will be asking for it straight back if the charges ever should show up. Make sure that all of your communication has been documented.

If the person handling expenses is even the slightest bit reasonable and rational, this should be no problem. He/she has probably run into this several times before.