Generally speaking, if you can easily reproduce the issue, it's a bug. I would still point out, that with the timeline it is REALLY EASY to create a layer with a single frame duration and have it not be visible based on the zoom level. For instance, I have a 27 inch display, if I create a 1000 frame project with the Broadcast 1080 preset, scale my document slightly and set the start/end to frame one, the layer looks empty. It's not until you zoom in that you see it is not. If you are on a smaller screen this is even more likely to happen, just because of screen real-estate.
Additionally, i've had times where I change the duration of the project (shorten) or drag a layer with a trimmed effect/behavior so it is outside the duration and had the layer element "disappear". I'd always start by checking these things. In a case like this.
As rowie302 said, then come here. Share your issue, give lots of details so people can try to reproduce or help you figure out the issue. (That's why we are all here 😀). If you can get others to reproduce*, then you may have a bug, and your can send in Feedback with the details.
*fwiw inconsistent reproducibility does not mean there is not a bug, it could just be REALLY hard to reproduce.
cheers!