Quite a coincidence - at the Marriott Crystal City in Dec 2001 - I never got a Plat gift either. I remember only because I had just become Plat. earlier that month -and was excited to "use all the benefits" - I asked 3 diff. times, called the front desk twice and once went down to the front desk. Each time I was assured it was on its way. This was before the choice/guar. so we are talking "the box" here. Anyways - I was FINALLY given the box and $25 credit on my account (I watched a movie I think).
Something about that hotel... Anyways - in this case - I would call the GM and ask to be comp. If you don't get anywhere - call the private Plat cust service line (# on website) and ask for service. Good luck!