It's been long since I was trying to find an old Scratch project I had made back in 2016, a good old OS simulator. With Vexento music in it, I was 9 and I called it Byte OS.
I had deleted it later on because, at the time, I felt it was old and useless, but now I just wanted to see it again.
I searched through old files to try to find anything remaining of it. I didn't find any project file, but... I found an HTML file, with a Phosphorus embed of the project... which so contained the ID of the project!
And from this, I got to the old project page as it was before, with the project half-broken but intact, simply by typing the proper URL. I'm so happy to have found this again.
So it turns out that Scratch projects are never really deleted from the website... just like unshared projects are actually publicly viewable using another tool. They just change a property to make the project
notvisible. And you can still edit your deleted projects if you wish... but you can't share them.
And, maybe this is an isolated case but, I could download the project file, but I wasn't able to reupload it to another project.
So if you want to see this old thing here's the sb3 file (why would you want to?)