Without more info and clearer images, I'm going to make some assumptions about what you're trying to do. From the blue background in the lower image, I can see that we're looking at a Smart Bones Action timeline. Could it be that the 'missing' keyframes for LegWarp are on the Mainline? Double-click...

Hello! I have a character set up with some actions using bitmaps, bones and warp layers. Suddenly, one of the warp layers have completley gone missing from the timeline, and there is nothing that seems to make it appear again! https://i.imgur.com/0g6fByJ.png This is the layer in question. https://i....