you have possibly hidden columns or you are working in the Ray-traced rendering mode, or you need to learn how to use the little timeline icons at the bottom left corner of the time line. It's impossible for me to tell exactly what's going on without a screenshot of your whole project. You can just snap a screenshot and drag it right into the reply field on this forum.
Twirl your mask settings up and then twirl them back down again. It looks like you just pressed U to reveal all properties that have keyframes.
Alternatively, you can press MM to reveal all mask properties (but you have to be fast otherwise it thinks you pressed M).
Forget what I said. Rick's got it!