Did you happen to print off a copy of your itin showing the upgrade request pending? I try to print off a copy of my itin anytime something on it changes, and I keep the prior copies as an "audit trail" of sorts. You may want to take a print of it right now, just to have it in hand before they start mucking around.

FWIW, I would also log an email to the 1K desk explaining the situation. Maybe they can intervene somehow before your departure. At the least, you'll create a written record of the situation with United - while they still have time to remedy it. Good luck.