Worried I'll pick up stomach bug?

hello all, i have a phobia of being sick which doesnt help at all -_- i have avoided stomach bugs (vomiting, watery stools you know) because i hate having one and hate giving it to parents i hate seeing them ill it really makes me upset so ive avoided it for at least 5 years now. ive had bad colds but they dont bother me. anyway back to the question, today a girl was sick at school. she told the teacher she was experiencing bad stomach pains and layed on the bean bags for about 10 min (NOTE im not her friend and didnt get face-to-face close id say about between a 9ft radius) then she was sick in the toilets. my school is basically a small hut only has 2 classes for special kids who have problems. i didnt go into the toilets when she was sick nor did i touch anything she touched. what im worried is can i pick the bug up if i go out the same door as her? like airborne. the door was left open so i didnt need to open it. sorry for the stupid long question but i want my mind put at ease as im terrifed off these bugs, ive put my hand in my mouth a few times but havent touched anything except the mouse for a pc at school and she didnt use it so.. thanks :) BUT.... my teacher was sat near her today and used the same pc as i did, so will i catch it????? or does the teacher have to be ill first before i caught it?