Thanks everyone for the feedback, support and comments.
I don't regret the post, and I think it has value as a warning/reminder, but I think my time would be more productively spent moving past this.

As several have noted, it's a hard-learned lesson of how expensive 'FREE' can be.

After s3m comment on the accounting, I can appreciate the Sheraton's position and hold no further grudge with them.
Marriott, on the other hand, [insert standard never going to stay there again rant].

It's just a bad policy for this particular situation.

Thanks all.