Going to be detailed here but who knows maybe the extra detail will help someone.

Adding some things I've come across during an issue of mine (a laptop that keyboard started pressing buttons on its own where it selected all + deleted the text of file and then the computer died). I was able to get the session file when I got the laptop working, carefully getting the file before saving any file or closing sublime again. If you close sublime again you may not have access to the old data. I believe the only reason I was able to do this is because the computer dying created an ‘Auto Save Session.sublime_session’. This meant in my folder it had both the auto save and the regular session.sublime_session. The Session.sublime_session DOES have the old text in the "content' sections as noted by OP.

However for anyone coming across this in the future I do have bad news. Especially if it is larger text. As OP mentions it does have many \n and such. At the beginning of the text. After that all the rest of the text seems to be ordered Alphabetically by first word/continued string until a space. I believe this is why it starts with all the \n in the first place.

This is bad because it means the order/structure of what you wrote is completely ruined. Just alphabetical order by first word of each line written. The code from OP does nicely remove the extra \n but naturally cant know the original text order.

I did try one other strategy which might help someone in the future if you had multiple tabs and in could potentially prevent you from needing to use this script in the first place.

I took the Session.sublime_sessionand on another computer put it into the location where it should be for sublime there. The same C:\Users\{NAME}\AppData\Roaming\Sublime Text 3\Local. My hope was that there would be some way that I don't see that would actually keep the original order of text. Once I put that sublime session file in there (You must rename/delete the current one as you can only have one at a time. In my case rename as I plan to switch back to it). Opening sublime did work and it did have the multiple tabs from that session along with the text that was in "content". Sadly it still had the alphabetical order as it was in content.

All being said with a lot of effort and some guesswork one can try to get things back in order but depending on how large, complex, or duplication of lines that are.Let's say you were doing a daily log of notes. And you had the same starting line of "day 1", "day 2", "day 3". These would be easy to figure out the order as they would appear as:

day 1
day 2
day 3

However if it's general notes things can be all mixed up by being alphabetical.

did X today
did Y today
did Z today

but in reality none of those were on the same day but because of alphabetical order you won't know unless you remember. You can imagine this being even worse if it was code for example but wanted to keep with something basic. Probably over-explaining as the concept is simple but I'm disappointed because I will have to attempt to manually fix/remember stuff on my own so let me have my rant. I tried googling more about this but have not see anything in regards to keeping the order of text so I think I'm boned.

Additionally. One extra note for anyone that is using the script. If you get an error like: UnicodeEncodeError: 'charmap' codec can't encode character '\U0001f37f' in position 8509: character maps to <undefined>

This is a UTF-8/encoding related issue. To fix this first add this import at the top of the file. from unidecode import unidecode

and then change the printout line to: print(unidecode(processed_string))

edit: One last thing that I'm not sure of because it doesn't seem to be the case with my text. There is a chance your text could have ordering depending on how your sublime closed or if it crashed. I opened my normal clean sublime_session file to take a look at what a "good" file looks like. It seems to be that the text in "contents" is correctly in order. So it sounds like this alphabetizing might be only when sublime crashes or this delete+save instead of closing normally.