Having forgotten to cancel a reservation or two over the past couple years and being charged as a no-show, I can confirm you do NOT get MR credit for the no-show, even though you are charged.

There is another thread on the Marriott board about doing a CY meeting for $100 and getting credit for ten nights. That may be your best option.

Another thing to consider - if you can find a cheap published rate at a FS, Ren or JW near you for a weekend, you can use an EEO certificate for the second, free night. You will get credit for two nights. I've found some rates well under $100 and been able to use the EEO for a second night. The best I've done is $56 for a night, with taxes, with the second night free, for an effective rate of $28/night. While only Plats can access the certificate, it's transferable, so any Plat can send it to you.

Also, if you have been Plat for a few years, and are only a few nights short, you will likely be maintained at Plat for next year.