At some point closing the file and reopening it was not making it appear even on the startup layout.
I found some thread that was mentionning this (thought i was crazy!) and created a button to which i attached the script to make the menu line appear. But often, it would not happen on the same layout so I had to go to the home layout to find my button. So I put the button on all the layouts. But I am curious as to why does that happen?
At first I thought it was because sometimes I am on the print preview window which is a floating and doesn't have the menu. It does not explain why sometimes the menu disappears from the main window.
I'd like to figure out what I may be doing to cause it so I can stop doing it!