That's what I suspected.
If you are correct, it's not that your policy was cancelled two months ago. In fact, chances are from what you've said, that they've only been cancelled a very short time - possibly a matter of days.
This is what happens, and trust me, I have seen this process more times than you would believe from the insurance carriers side, the plan administrator's side, and once in a while even the employer's side (we fired the accounting clerk

):
1. In mid November your employer received the bill for the month of December. It was due December 1.
2. For whatever reason, almost always because of cash shortages (your employer is covered on that policy too, why would he cancel it deliberately?) he doesn't pay the bill.
3.) On or about (give or take a few days either way) December 15 your employer receives a bill reminding him that December's premium has not yet been received. He is also at that time billed for January.
4.) A few days later, probably a few days either way of December 22, the employer is notified that if December's premium is not received within x days (probably by a date between January 1 and January 10, depending on the insurance carrier) the policy will be cancelled.
5.) The premium is not received (there's a lot of cash flow problems at the end of the year) and coverage is terminated RETROACTIVELY to November 1. Your employer couldn't tell you about it in November because it hadn't happened yet.
Following the usual procedure, you haven't been told about it because your employer is running around trying to get the policy reinstated and he's hoping you won't find out before he succeeds. (BTW, unless he has done this several times before, he most likely WILL succeed.)