This has been a problem for me for at least the last 2 years. Upon closing firefox android, every 1-2 months it will delete all "restored" tabs. Which I usually hover around 50. I didn't notice this part before now, but to combat this I turned up the recently closed tabs queue to 200 to try and save these non restored tabs. When it happened this time the recently closed tabs queue was also deleted and empty. History seems to be fine though My only chance of recovering these tabs is to immediately put my phone on airplane mode and use another computer to save the synced tab list. Unfortionately, many times I am not fast enough to beat sync and my tabs get lost forever. To trigger this bug you just need to force close Firefox from the task switcher screen in Android. I have not been able to deduce what other factors will trigger this bug. Is it possible for the current tab and recently closed tab databases to be corrupted on a force close?