This is how to get the problem: 1) Open Firefox 2) Create multiple tabs 3) Pin some, leaving at least two unpinned 4) Move one tab out of the window, creating its own window 5) Close the original window first, then the one you just created 6) Open Firefox again If you follow the steps correctly you'll notice that the pinned tabs are no longer there. I find it very frustrating, and this has happened to me way too many times. The tabs should remain there until you actually remove them yourself. Proposed solutions?: -When you move a tab out of the current window to put it in its own window, it will also copy the pinned tabs over to the new window. -Have a spot for the pinned tabs in settings, so no matter what you do, they will come back when you reopen Firefox, and will not go away until you actually unpin them yourself.