This is a longtime issue that continues not to be addressed in the app. I've finally documented the specific scenario where this happens to me (however, it might not be the only scenario where this occurs.)
I believe this is primarily happening when I turn off my Shield without backing out of Channels, which is what I do with voice control via Alexa and a Logitech Hub.
When I go to watch the Shield the next time, upon starting it automatically launches Channels, however if anything has been recording you will not see it in the library. Furthermore, if you select a program that has recorded or with recording in progress, it will only go to live, not giving the "Watch Recording / Watch Live" prompt.
The way to fix this is to then back out of Channels and re-enter Channels. I've put up a YouTube video showing this:
Can this problem be addressed?