I would. I am one to generally give the hotel a lot of wiggle room on small issues like housekeeping missteps and the like. However, the thought of returning to the room in anticipation of eating what you'd set aside earlier -- only to find it both gone from the room and then to discover it largely eaten out in the hallway is sort of a slap in the face!

I can well imagine that sort of thing could easily take the bloom of one's day.

And, I do think that "surprises" such as this should, indeed, shrink in direct relation to the rate paid for the room. (i.e. if I pay $69 at a Houston 4 Points, I'll put up with more poor service than I will at a $400 room overseas.)

At a minimum, the GM should be aware of what you found -- which would surely indicate (but not prove) that your food was consumed by the housekeeping staff.