Oh? And how would he be the one to know? He can't sense anyone that far. Cerebro was out of commision since its parts were stolen by Stryker and ended up under water at his base, so he couldn't use it to find anyone even if he wanted to. Jean herself wasn't sure what happened, just random flashes of memory. He didn't learn anything by probing her head while talking to Logan either. Plus Xavier can't sense or scan people who are unconcious or in a coma unless he's there in person and makes physical contact. The movie leaves a big plothole at just HOW Xavier found out. My best guess is Logan told him so and he believed him. I think it went something like this: "Charles, we couldn't find any sign of Scott." "Did you do a thorough search for him?" "Well not really. We forgot all about it once we found Jean." "hmmm, I see. But you found his glasses?" "yeah. Floating in mid-air." "It's obvious then. Jean must have vaporized him" "damn" When he felt that disturbance, he didn't know anything specific except that something BIG happened at Alkali Lake. but he didn't sense something specific like Scott being in danger, otherwise he would have told Logan and Ro before they left. None of them knew that Scott went to Alkali Lake. In fact they were surprised to find his glasses there (no specifics on whether they found his motorcycle). So the whole matter seems pretty vague. Neither the movie audience nor the chararcters in the movie could determine for certain what happened. And I'd get provoked too if someone accused me of killing someone and I didn't. Granted I probably wouldn't lift my house off its foundation and turn the other person into sand, but I'd still get mighty upset.