Open one of the auto save a back up copy you made.
The issue you are facing may occur if the sequence is not loaded on the timeline. In this case, please try to search for your sequence in the project tab (You may type sequence in the search bar of the project tab, this will populate all the available sequences in that project).
Then you may double-click on the desired sequence from that list and it will load it on the timeline.
Hope it helps, let us know if you have any questions.