I had used FireFox screenshot, twice, during the same browsing session, and when I tried to use it a third time, the icon disappeared when I clicked on it.
This was the easiest screenshot app that I had come across. Getting the shot I wanted was easy and I could store it in a cloud, albeit temporarily, but saving the image on my pc was very easy,
I have this issue as well. No way to get the icon back. In about:config, hide the feature is already set to ‘false’. It’s a pity, I really like FF screenshot.
If you’re using Firefox 57 it has been moved underneath the Page Actions menu (the 3 horizontal dots in the URL bar). If you see it in that menu, you can right-click on it and add it back as an icon if you prefer.
Thank you so much!
i was so confused where it was disappeared.
Same here 
I was just using it 20 minutes ago
