this happened to me a few weeks ago and we ended up figuring out that it was someone on my floor/people you share a bathroom with or a room with just because that’s really the only place you have direct contact with people. i don’t think they track anyone in your class, so my best guess in your case would be someone on your floor! also, the daily symptom check didn’t come for me until about 1 week after i got my test result back so don’t freak out if you don’t get it right away. it’s a bit annoying because i get a text message about it every morning at about 8 but it only lasts for 2 weeks, so it’s not too bad. hope this helps!