Norm,
I posted a similar issue a few months back.
And yes, the entire bloc disappears from the project and layer tree.
I noticed that no matter how careful I am with my BLOCS projects they always reach a point where the project file becomes unstable and starts exhibiting random behaviors like disappearing blocs, opening a recovery file at startup, image sizes a different for the exact same size files, etc.
I really like BLOCS and want to continue to be able to use it but I can’t afford to have my projects randomly fold and become unstable. I keep my Mac very clean and do not run all but the essential software needed for my business.
Regards
M@