Welcome to FlyerTalk!

While Presidential Platinum is CO's highest status, it's not CO's highest criteria for upgrades.

A Gold or Silver on a Y or B fare, or a Platinum on a Y, B, or M fare will trump a Presidential Platinum on a fare other than Y/B/M.

It's possible there were lower Elites on a higher fare bucket than you on the flight.

That said, with five (5) open seats, it's possible that you'll still get the upgrade anytime between now and departure.

Though it's still possible that you may fall victim to CO's "tens of dollars" upgrade program. CO will sometimes aggressively market Y/B/M upfares to Elites at checkin, sometimes for as low as tens of dollars, so if there are enough of these takers, they could possibly trump your more than $30,000 in annual business.

Good luck!