Complicated and huge work in Illustrator

I have an order from one of my customers in Adobe Illustrator CC 2018. I have been working on it during 5 days, yesterday I almost finished the work. I started saving .ai file and Illustrator was closed. Almost a day of work was lost after opening image. I hope the members of this community might suggest something to get my data back.

 

I would go into Preferences and hopefully you have AutoSave checked and then see what folder is used for those autosave files. I don't use Illustrator, my son does, and I've seen how much work one can loose. I always have AutoSave turned on in AutoCad where it works very good.

 

Another ways to .AI files restoration is below in guide. One more thing, if you need more variants, you may read it on this query like .ai file repair software in search engine...
1. Close Adobe Illustrator.
2. Right-click on the Windows "Start" button, and click "Open Windows Explorer, then the file manager opens. Navigate to the AI file to delete.
3. Right-click on the AI file to show the context menu.
4. Click the "Properties" option. The Properties dialog box opens.
5. Uncheck (clear) the checkbox next to the "Read Only" option in the File Attributes section.
6. Click "OK," and close the Properties dialog box.
7. Right-click on the AI file, and click "Delete" from the context menu. Click "OK" to confirm the deletion. The AI file is deleted.