I have encountered what appears to be a bug. I plan on doing further research when I complete my current project but feel this is a significant enough problem that I should mention it to alert others and to find out if anyone else is experiencing the same problem.
System: Premiere 14.9.0, Apple Mini/M1/16GB Ram, Adobe fresh install on clean system
Problem: sources disappearing from project window (image attached)
Example: Interviews in folder (project folder structure mirrors hard drive organization) are edited into a first assembly. Project Saved As v2. That assembly approved, move on to b-roll. After adding b-roll I decide to return to interview footage but when I toggle open my Interview project folder it is empty.
When I select the source interview in the timeline I can perform the match frame function to load it in the source monitor, but it still does not reappear in the project folder (and all unused sources are completely unavailable). When I select the source interview in the timeline and select Show in Project, Premiere cannot find the file because it doesn't exist in the Project window. When I select the source interview in the timeline and select Show in Finder it takes me to the source in the finder.
My current theory: Premiere is getting confused during Save As and, for some reason decides to only display some of the sources in the Project window after a Save As.
One test I plan on performing is going back to my first assembly and trying two different methods of saving: Save as from within Premiere, and duplicate and rename the project file in the finder and open the dupe. For now I'm working around the issue.