Yes, the pellicle is critical to maintaining control when smoking fish and the lack of an adequate pellicle allows the moisture to evaporate from the fish and cooling it.
Evaporative or adiabatic cooling works because evaporating water takes a tremendous amount of energy with it when it goes. That energy is called "latent heat of vaporization" and is 970BTUs per pound of water. It takes quite a lot of heat to overcome that... So the fish continues to cool from the surface while heat in the smoker attempts to keep up with it.
The pellicle seals the surface and reduces that evaporative cooling dramatically.
Fish takes a lot longer than a few hours to go bad at room temp... but cooler is certainly better and the treatment the fish got prior is also important to how room temperature will affect it. It also is being cooled adiabatically but due to the lower temperature of the product it dries faster than the water inside the fish can be mobilized.
With only 15 degrees difference between fish and ambient temperature and active cooling going on there is little temperature differential to add heat to the fish.
And of course that brings up the bigger question of what the temperature actually was in your smoker. Say your smoker thermo reads 5* high and the probe reads 5* low... Hard to get much temperature gain there. How sure are you that the smoker temp is correct? I have seen smoker temps that read more than 25* off actual...
