Hi Luka!
Thanks so much for reaching out! We recommend always saving and publishing Storyline projects on your local hard drive (typically your C: drive) when possible. Working on a network drive or an external USB drive can cause erratic behavior due to latency. For example, it could cause file corruption or prevent you from saving changes.
As a workaround, I'd like to recommend you check your temp files to find a working version that could include this missing scene.
Here are the steps:
1) Open this folder in Windows Explorer: %appdata%\Articulate\Storyline
2) Scan the contents of this folder for a file that starts with the name of your project. If you find one, copy it to your desktop. If you find more than one, copy the latest version to your desktop.
3) Change the file extension of the copy on your desktop from *.tmp to *.story.
4) Double-click the file to open it in Storyline.
I hope that this helps! If you're still running into trouble, we'd be happy to take a closer look at your .story file in this thread or privately in a support case.
Looking forward to hearing from you!