1st time smoking

Food preservation is a complex science, and you don't want to shoot from the hip. For instance, given the relatively short time in the brine, the salt etc. probably wouldn't make much of a difference.

The key question is the temperature of the fish when you discovered your error. The so-called danger zone is 44-140F. That's when bacteria and other pathogens are at their most active. The rule of thumb, for safety, is that the food can sit in the danger zone for up to four hours, and still be considered safe.

So you're question actually is: were those conditions obtained. Given that the fish was still partially frozen when you started, I would guess that they weren't, and the fish is likely safe (I'm assuming you got it back in the fridge when you discovered it). But only your thermometer knows for sure!!!