@ Misters hehehe you are correct.
Odd to have a pectoral fin go missing. I am either missing something or not thinking clearly, other then the fin missing, is there anything else going on with him? Sorry.. so tired right now. If it is just a fin, he will grow back, just keep the water clean (keep on your regular water change schedule) and he should be okay. As mentioned before, if he is having trouble swimming to the surface, lower the water to about 4 inches or so to make it easier on him. Stress coat will help promote fin growth, so if you have any you can add that in, but it's not necessary. Poor Ice!