I had one that came true.
A friend gave me 2 cherry barbs that lived for around 9 months before one of them died. I held off on replacing him. For another year or so the other one would hide for the longest and at times I thought he died too but he would show up later.
I got worried later that if I got him a buddy then he would die off. I finally broke down and got another one. 4 days later, I found a dead cherry barb. The very next day I found another body...ugh! I really wanted to buy 2 or more but that was the last one the store had.