Take a look at how another member of Brave Community, recently recovered passwords::
‘NOTICE: Unexplained Data Loss Issue - #175 by Lyte’
Also, study the general idea:
‘Brave passwords disappeared after computer crash, and force-restart - #2 by 289wk’
Also, a Chromium issue to read up on - though not your immediate concern:
‘All passwords are gone in Password manager - #3 by steeven’