If you show your military ID Card at time of check in you should get credit for the stay. I have used it for over 10 years and it has worked. When you "book" the room on line use the military discount.
I am an ARMY Wife and I am on top of my points. We've pretty much earned our Platinum Level through all the TDY's my husband has gone to (He usually brings me along when he can). First, are you making the reservation through the marriot.com website? If so, your Rewards # and your name should be already on the Reservation when you book the room. You also have the option of reserving the room with the Government Rate already included (sometimes I opt not to make the reservation with the Govt Rate as it can be a lot higher than the hotel's regular rate, ie..Maryland, VA, etc). Keep in mind that your name and your Marriott Reward's number that was assigned to you MUST match the reservation, otherwise, if either is missing, you will not get credit. I've had that happened before. I hope this helps. Also, don't forget you can get retro-active credit for missing stays. You can do this through their website. However, your name had to be on the reservation as well. Thanks for serving!
If you are making the reservation and are paying for your stay, then yes you will get credit. This includes being reimburesed,once travel has been processed through your finance dept. at your place of duty, once you complete your TA. If you are going TDY and the reservations are being made, paid and distributed by a third party then no. Sometimes rooms are blocked out and you just happen to be one of a number of rooms reserved. If the hotel so wishes, but highly unlikely, it can give you credit for the stay, even though your name does not appear on the bill.