I was giving weapons to Izuna to level her up, and accidentally clicked on my Poison Oubai to give her. It was favorited, so the messaged popped up saying I couldn't do it, and like a complete dumbass, I simply uncheck it from favorites, when I meant to unselect the weapon itself from the list.

So now my level 100 Poison Oubai, with its maxed skills and two maxed Ougi, is gone for good. Damn it all. I really, REALLY wish there was an undo action button or something.

That's terrible =/

I did a similar thing as well, and probably like you, instantly knew what had happened a second later. It has something to do with the constant double user confirmation, like we're more inclined to dismiss things the second time around.

But yea, an undo button would be nice for a lot of things.

I had found out when I almost made the same mistake twice in a row, but with my bow. I unchecked it from favorites, only to realize what I had done and rechecked it and unselected it like I meant to. Then I noticed what I had done with my Poison Oubai and when I checked to see if I still had it, hoping, I realized it was gone.

I'm still kicking myself over for making such a mistake.