The second possibility is Magus. While he wasn't a team player, and I really can't see him caring enough about his old comrades to try and save them, I also can't imagine either Kid or Schala not asking him to try and save them, if Magus ever found either of them. Since the whole purpose of Magus' life was to destroy Lavos as revenge for taking him away from Schala, I think that even though he doesn't care about his old teammates, he'd still try and save them if Schala\Kid asked him to. I like this second option better, not because I think Magus is cool (Lucca is so much cooler), but rather because it does a better job of tying Chrono Cross in there. There is a small amount of evidence in Chrono Cross that the *official* way things went is that Magus lived through the end of Chrono Trigger; specifically, in the children's drawing of Frog he was still a frog, implying that Magus wasn't defeated and the curse wasn't broken. The other thing is that in her letter to Kid, Lucca mentioned that Janus was searching for her - which is not something he could very well be doing if he was dead.