This kind of saying seems reliable... I know a kid skipped the 'crawling' stage, he has some sort of behaviour problem. FYI, he is a left handed guy....
Don't worry. My son did not crawl at all and he is now at F.3 and he has been performing quite well in school. He does quite well in other areas as well, like music and sports.
I was also worried when he was a baby, but it seems okay.