Yep - good advice, newf.
Food shouldn’t ever be thawed at room temperature - I know a lot of us do it, though.
As to whether it was still good or not, it would depend upon how low a temperature the salmon reached and how long it stayed below 40º before it was refrigerated. Time and a friendly temperature breeds bacteria.
If it was still partially frozen before it was put into the refrigerator, three days later is still about the limit for meats.
Then the cooking time - did all of the fish reach a high enough temperature and stay there long enough to kill food-borne bacteria and virus? Fish should flake easily with a fork when it’s been cooked enough.
And did the cooked fish go back onto the unwashed plate where the raw fish was prepared for cooking or did it contact any other utensils or surfaces or hands which may still be contaminated with juices from the raw fish?
He’ll probably be fine - but you’ll know for sure in another 12-24 hours. Food poisoning does not act right away - it has to incubate for 12-24 hours before you begin feeling symptoms.
Try not to worry though. People have been mishandling food for a long time and usually without serious consequences.
Just don’t eat it yourself and don’t let a child eat it. Their systems can’t handle some of the bugs that adult bodies learn to fight off.
(former restaurant manager)