23.98 project settings switches to 24

I have a project I recently started using UHD 23.98 footage. I took the time to set the project and the timeline to the same frame rate and resolution. I spent yesterday just going through footage and everything was fine.
Today when I reopened the project, it's telling me the project and timeline was set to 24 fps. I know I did NOT set it that way...is there anything that could have overridden it? It seems like I've had this problem before, but I can't replicate it on a regular basis.

I'm not aware of any way for this to change on it's own, or even intentionally once media is imported.

Without being there, my best guess is Observer/Operator Error.

You opened a different project. Or the Project Settings haven't changed.