If you did all that you're supposed to for qualifying for the Platinum arrival gift and you didn't get it, then they owe you some $$.
Straight from the Platinum terms & conditions:
7. Guaranteed Platinum Arrival Gift is available at all participating Marriott Hotel brands. If guarantee is not met, guest compensation applies (see below):
|Brand|| Guest Compensation*|
| JW Marriott, Autograph Collection, Renaissance Hotels, Marriott |
Hotels & Resorts, Gaylord Hotels
| $100 USD|
| Courtyard (U.S. & Canada), |
SpringHill Suites, Residence Inn
| $50 USD|
| AC Hotels, Courtyard (outside U.S. & |
| $50 USD|
| Fairfield Inn & Suites, TownePlace |
| $25 USD|
| Marriott Vacation Club|| $100 USD|
Go to the front desk prior to checkout and get 'cha some cash! If they give you any **** about it, tell 'em to look at Marriott Rewards® Terms and Conditions
As shoeman stated in jakeal's link above, he has received the guarantee, but he also stated, which I concurred, it's a major pita and a guarantee with no teeth as vacation0's case demonstrates. We all believe vacation0, and now after five or six extra steps, the property quite easily states, "oh, those points were posted", i.e. no guarantee payout.
Bonzaflyer is correct, vacation0 is owed the guarantee, and he/she just may get it when/if the Front Office Mgr. "reaches out" (or he/she just may get an ever so polite runaround), but look at the headache caused over a no brainer, 500 points.
Keep us posted vacation0 of the outcome and good luck - you deserve the guarantee.