Response to "Did you check your stash" - Yes, I checked my stash and every character's inventory. "Tidefall" was gone.
Since patch 3.01, the issue still occurs, but it does not appear to delete the weapon now - which is an improvement. See attached screenshot.
note - i previously equipped a junk item in Kana's weapon slot 3 to better identify when it happens again in the future.
I have also included the most recent "output log" that existed just after adding Kana to my party & saving the attached screenshot.
Hopefully there will be something of use to you guys to help track down this issue.
Also, this seems to occur more often when you have switched around multiple members of my party, like is common when you have to go through each member looking for an item you previously gave them.... but have forgotten which one it was.
output_log.txt