Frank Horrigan is dead, that's pretty sure. The person he was is dead, the parts that he consisted of, flesh and machinery, is also dead. No trace of his DNA to be found, his cut-in-half body was either completly incinerated by the atom blast, and/or sunk to the bottom of the ocean (or well, I don't think organic material ever sink to the bottom of the ocean, it gets picked clean by every living creature on the way down until what little that may remain is just dust particles that forms a carpet on the bottom of the ocean... I kinda drowsed infront of a show on Discovery channel once, about the bottom of the ocean). But I think it's more likely he was incinerated by the intense heat from an atomic bomb, he was reduced to atoms himself. He's dead, gone, has kicked the bucket, has siezed to be, he's an ex-Enclave-robot-mutant.
Though what is there to say he was the only mutant super soilder the Enclave made? I mean, he proved to be very very efficient at what he did... except for activating the oil rigs self-destruct program, and kill of the entire Enclave (or so we thought) while
we still managed to escape.
So, tip for the Enclave: if you build super soldiers to do your dirty work, do not give them the self-destruct code to your main HQ