Workflow and style that suddenly disappear

Has it ever happened to someone?
Yesterday I was demonstrating when suddenly a style disapear …

I can doubt myself … but it is very unlikely that during the demonstration, I will go into development mode, then in style; that I remove the “background page” style
I am the only one working on this Bubble solution.

If you are on paid plan you can save multiple version of your page.
Also i would check page settings maybe you have set mobile version of page that doesn’t have these elements. Or set to be invisible