I just experienced one of those rare sudden disappearances of a Private Window.
I’ve reported it happening before. I don’t have a clue what causes it.
I just go to the Window dropdown to open one of the window’s tabs and it’s no longer there. It and all of its tabs have disappeared.
Gone without a trace. Never displays in Brave’s crash history.
Brave v. 1.58.109 Chromium: 116.0.5845.163 (Official Build) beta (x86_64)
Mac OS Mojave (v. 10.14.3)