I’m experiencing a bug similar to this one, which was reportedly fixed in 0.0.17, with Obsidian 1.0.5 (appears to be latest version) on iOS.
I’m using the Minimal theme.
I was able to restore the menu once, but currently neither switching back to the default theme, quitting the app, or completely reinstalling the app brings the menu back.
Will post steps to reproduce when I get the menu to re-appear.
There’s a “pin” button on the top right of the left sidebar that pins the sidebar open. In the “Minimal” theme, this pin is removed, so I didn’t know it existed. Somehow I was pushing this button.
To revert, I needed to activate the default theme and tap the button again.