This is my experience as well. Saw it once, never seen it again. The only way I can think of to fix it would be for someone who understands the format of the save file to take a look, but I have no idea who could do that other than Hrelease.I'm on day 323 and I saw it happen once only and it happened just because the game had to introduce Mary.
Its only purpose was to introduce Mary. You will never see it again unless the Author introduces some pharmacy events.