When it uninstalls itself, is it sill listed in apps from the Settings menu?

Thanks for replying Guigs. I Didn't look apps from settings menu last time it happened. I will now. But I would say no because google play store shows "install" replacing "open" for firefox.

I have not heard of that happening before. I have done quite an extensive search and found nothing Have you run out of RAM or memory, and your phone is deleting it because of that?

I'm using Clean Master and Advanced Task Manager showing 31% Storage used and 72% RAM after one week without restarting my phone. John, Do you think any of those programs can uninstall without warning? Well the good thing is that I'm 8 days with no problem with firefox. By the way, this problem happened 4 times between January 5th and 18th. Thanks.

Ah I tried Advanced Task Master, and the whole time, funny things were happening with the phone. I would say, its a high possibility if you have not made out the rules correctly, that might just happen. I dont know the other app though. Try uninstalling both, and see what happens. :_

I'll do this if this problem happens again. Meanwhile I'll be monitoring both of them and check any updates. btw, I don't have automatic updates enabled. Thanks for your help John.