This mission I happily play again because I am so close to the end of the main campaign. On wednesday I was in the sewers and trying to find a way to the brodcast tower.
When I recovered the file it was dated 05.07.17 this week and I completed the game yesterday (did not play it on thursday). I also read some people mention recovery apps and one such app became my sanctuary, mainly Glary Undelete. Some people recommended downloading other players savegames but these were so overpowered (and also cheated) that I had this feeling of not playing the game myself. I searched on Google for everything that could help but it looked as I was doomed to start over. Because of this mistake I either had to start over which in my case meant replaying about 87 hours (I spent much time exploring). In this thread, I described how I 'managed' to delete my save file in The Following which resulted that the savegame from the main campaign was deleted.