@Lhadolma I looked at all the reports and I looked to see if there was a hidden transaction for that hotel, I didn't see anything. Has this user checked their credit card statement to see if there is a charge for this hotel on the statement?
If there is a charge, then for some reason it didn't get included in the file that gets uploaded to SAP Concur. To ensure the charge gets paid, what you could do is submit this expense as Cash by changing the payment type. This will then allow the user to receive a reimbursement that they can then send in a payment directly to AMEX. Before doing this, I would get approval from your manager or someone in Finance or Payroll. Explain the situation so they know the card charge never came in.
On the expense entry itself, if you get approval to do what I explained, use the Comment field to also explain what the situation is. This is really about the only option you have, unless your Finance or Payroll departments tell you something different.
