You deserve your points back, and probably your SNAs too, although the latter might be difficult. Did you mention to Marriott that the reason the room was changed was that SNA's were applied? They should see 5 were removed from your account for that stay and realize it wasn't a change you made to the reservation. You said you didn't mind the SNA's being used anyway, which makes sense as you intended to use them all along.
I'm not saying you should HAVE to do all this, just that it might be the easiest way to resolve the issue and get your points back. Obviously Marriott's system isn't reading the sequence of events correctly or not tying events together.