I always am upset over something like this. It takes me more time than I think I should mourning, but I do...
I got a catalina goby in my tank once, had him for almost a year. Didn't do the research as they are a 70°F fish as well. One day, gone. I knew it was going to happen once I read up on them. Let's put it this way, my GF likes to buy the "pretty fish" she sees and then doesn't heed any warning. I remember this one in particular, "it won't do well" I said, "it's a colder water fish" I said, "It's not going to live long" I said.
Although sad he perished under my care, there was no "I told you so" I said" going on; I know when to pick n choose my battles.
Sorry for your loss.