I've tried searching a number of ways and can't find a Factbook entry for just Mark 16:9-20. That seems like an oversight. It's definitely in its own pericope, so I'm not sure why the Factbook is not treating it as such.
I tried typing in the words "Longer Ending of Mark" and "Mark 16:9-20" and nothing comes for that specific reference. I get suggestions for all of Chapter 16 and for just vv.19-20 or vv.9-18. Weird that it doesn't treat 9-20 as it's own pericope.