Resolution
Was contacted by the GM at the Las Cruces SpringHill Suites yesterday.
He apologized for the problems I encountered, and augmented my Rewards Points balance nicely. The points posted last night, after which I received a confirmation e-mail from Marriott.
The GM also acknowledged my mother's illness (a nice, personal touch!).
Bravo to the GM and to Marriott!
And thanks to you for directing me to a speedy resolution.
^ ^