
Listen to the last answer.
Its likely that its going to two different spots OR you've got two different mileage numbers; one that is tied to your credit card and another, thats likely older, that's tied to miles flown.
Look at it this way - if you didn't have the mileage card from United...... you should be able to log in at www.united.com using the mileage number on your card to view your miles.
If you have a cc that accumulates miles... you should be able to view your miles when logging into that credit card.
But you've got a UA credit card, so the most I can say is that you've got a synching issue!
Try calling them again - if your simple explanation doesn't cut it... tell them, I flew on 10/01 from ORD to IAH please tell me where those miles are?
If you do have two mileage numbers they can combine those easy, that is of course, easy enough once they understand your issue...
Have fun!