Hello Johannes,
There's multiple safeguards for your Bible text that normally should have been set up and be used regularly.
Some of these are:
1. Regular backups of the local computer.
2. Leave the admitted percentage change low.
3. Export the Bible to USFM manually regularly and keep copies.
4. Connect to a Cloud system.
5. Connect the Cloud system to a git repository.
6. Letting the Cloud system email the changes to users.
7. Multiple local copies of saved chapters.
Based on the description of the situation at your end, it could be that option 1 can help.
If not then option 7 could help too.
More information about option 7:
In your home folder, say, /home/foo/bibledit/bibles, there the Bibles are stored and several copies of each edited chapter. The Bible books in that folder are numbered, where Luke is number 42. Then inside folder "42", there's the chapter folders of Luke. Each chapter contains a couple of previous versions of the chapter, in fles like 100000001, 100000002, and so on. These might help you to get the lost text back.
I hope you may be able to recover the lost text again soon.
Teus