The other possibility is that one of the third party scripts messed up. I have one to store variables outside of savefiles, and I have noticed it rarely, and seemingly at random, messes with variables it isn't supposed to interact with, maybe that's the issue (as it "remembered" the time you received the message in the previous save).
Deleting the "MyProject" folder can fix those issues, but it's probably not worth the effort at this point (and it's not guaranteed that's the problem to begin with).