The distribution should have been paid the following day, 12/18. If you didn't see more shares or cash by the morning of 12/20, call your broker. They can explain the delay.

I use Quicken, and record the distribution in it as soon as I get the numbers. That way I don't have to look at the lagging brokerage account until a few days later. Then I just verify the numbers.

It's really only a problem when you are reinvesting, and you want to liquidate the fund and they haven't recorded the reinvestment. You sell all the shares you had, then ta-da, more shares suddenly show up in your account.

In late November, it's a good idea to go to each fund's site, that you hold, and record the December ex-distribution dates and estimated amounts. That way you avoid the "what happened" shock.