Sat next to someone who got stomach flu the next day. Were they contagious? I used sanitizer but wiped my mouth w my hand 30 min later can I get sick?

Probably not. Stomach viruses are passed through contact. If you did not eat or drink after this person then you are probably fine. Theoretically if they touched an object that you touched, then put your hand in your mouth you could catch it that way but that is much less likely.