Running TC 8.0 x86.
Used the apps utility to check for updates, and saw two that needed updating - cairo (and another I forgot).
Performed the update and rebooted. Fifth browser icon went to bit bucket.
Notice fifth.tcz still existed in my optional directory, so fired it up from CLI, and it told me I was missing libGLESv2.tcz.
After a manual install of that library and a reboot, fifth is back! (I'm using it now). Love the fifth browser, so I freaked - just a little.
Trying to figure out if it was me, (most likely), or some process in the Apps update utility that missed something..