Hotfix for saving projects.
Do you use cloud save? If so the cloud service should have a version history you can recover it from. Otherwise you'll need to restore a backup...
AND I used stable release
This issue has not affected any stable release. It only affected r319, which is a beta release that requires people to opt-in to use it - the default version is a stable release.
No, I saved just like a file. I know, that is bad idea, next time I will save in cloud, but now my file is 0 :(
It was a lot of work
If you have any backups you've made, or if you set up Construct to make backups for you, there may be a file you can restore in the backup location. However if you did not make any backups, I'm afraid there is not any way to restore a lost local file save - unfortunately this may be a hard lesson on the importance of keeping backups.
Yes, but backup 0kb too. Good, I think so no ways to restore it... Will save in cloud next
always have multiple save version of your game