Look in the Project Panel for the sequence and double click on it.
Any back up files as in Save a Copy (to another drive)?
If you use the Save As an option to save the file and choose to replace your existing project file with the same name, Premiere Pro closes the project file and shows a blank workspace. Some users end up force closing Premiere Pro thinking it has crashed. On opening the project again, all sequences are closed from the Timeline panel and users assume that their work is lost on seeing an empty Timeline panel.
Workaround: To continue where you left off, open the sequence by double-clicking the name of the sequence from the Project panel.
To avoid the entire situation, either save the project file with a different file name or save it to a different location.
This is a known issue and we are working on a fix.