I don't know how else to explain it other than a heap of the media that I have imported into my project is missing from the project window.

Worse still, entire sequences are missing. They simply are not there.

However, they are open in the timeline because they were when I last saved. So they still exist, and even the media that I cannot see in the project window is still online and present in those sequences, but I cannot find them in the project window.

Bins containing sequences and media are empty. I am so nervous about this.

Nothing is typed into the search bar so there's no reason that items should be hidden.

What the heck is going on?

I have done hours of work on this before I noticed and now I'm worried that I may have to go back days to find a version of the saved project where this isn't the case.

Does anyone have any advice?

Have you tried opening one of the auto save project or a copy you saved on another drive?

Please wait until better brains than mine apply themselves to your situation and comment here. Sometimes when things seem to go missing, I reset the current workspace and sometimes they come back.

A suggestion was made to me here a while back when I got into a mess after a hard computer crash, as in went totally dead. The project would not load and would crash Premiere. The solution was to start a new project, and import the original project into the new project. That seemed to work but the bin was pretty disorganised afterwards.

maybe you have typed "space" in the search box of the project window by accident and therefore it will only show the assets that contain a space

Just a guess.

going back to a previous saved version isn't that tough - I'm assuming you have auto save on?