Always start your missing mileage complaint with the online vendor. If you don't see the miles in your OnePass account, odds are that the vender never sent them over. If the vendor says they sent them over, ask them for the date of transmission, and get the representative's name, then call 713-952-1630 and ask to speak with a partner liaison.
Remember that most vendors will not send miles over until the "return option period" on your merchandise has expired.