There can be so many bad occurrences with marines, but really cool surprises as well?

This year was a hard slog for my aquariums as I have typed, but out of that came a surprise.
I got rid of all my wrasse, soap fish and more recently from the tubs and just got to setting up the tubs again for some marine life breeding.
I haven’t fed the tubs since I got rid of the fish living in them and yesterday while starting to clean them out ready for new things to happen, out popped the bi coloured dotty back I got some time ago, I forgot I had it, so I dug around in all the rubbish in that tub to catch it out of which I was going to be cleaned out anyway and here was my old deco crab!
I thought I killed it months ago?
When I first put it in either just before I started back with glass aquariums again or about the same time, either way it was over 4 years back.
I just got it for pics and forgot about it, you see that day I had my first proper underwater camera for a month by then and a mate was kicking up lots of silt so I couldn’t get a decent pic so I took it home to take pics as I do from time to time with marine life.
So over the years I would see it off and on and I would take a pic of its current dressing up achievements with algae/sponge, its got real talent that way and that’s that, but while holding some life forms for a mate, the heat got so bad they all slimed the tubs and shut down my bio filer which is the current in the second tub.
Two busy days at work till I noticed this was going on and near all were dead in these tubs, I thought so any way. So the next day I checked to see how much life I had lost to clean them out and virtually every thing had recovered??
But my old deco crab was nowhere that I could find it, it was dead and probably in pieces like crabs do sometimes when they die, they fall a part and I was quite disappointed and that was months back.
While searching in that tub I lifted up this lump of algae to see if the dotty back was under it and it was the crab, the dam thing had lost all the original sponges, they obviously died off, but here it is with some algae I chucked in a while back, healthy as!
To this day I still remember that exact rock I turned over and saw this guy and took it home.
As far as i know it has never harmed anything and so its place is in the tubs till it dies and hope fully that will be of old age.