Reference not replying?

[Deleted account]

Hey folks, I'm sure many of you have been in this position, and I was hoping you could give me some tips: 

I've just sent in my MA application yesterday. The school gives references about 2-4 days to submit their letter, and one of my references have already submitted and I trust a second one to also submit his letter (the school asks for three). The third reference hasn't replied to the last two reminder emails I've sent him. I passed by a class he was supposed to be teaching this afternoon, and it seemed like he wasn't there, either. My friend got a reference letter from him before, but he mentioned that the entire ordeal was very stressful and the LOR was submitted at the very last minute. Still, knowing this isn't calming me down. I spent 4 months on getting my application ready, and I'm feeling really upset at potentially having my application rejected because he couldn't submit the letter. I'm planning on doing a couple things and was wondering if y'all had anything to recommend/ add on: 

1. I'll call his office tomorrow to see if he: a) has started yet; b) is sick and out of the office 

2. Depending on the response I get from him, I'll contact the grad admissions to let them know what's going on 

3. I have someone who might be able to help out if the reference flakes on me completely. However, this person is a PhD student who worked as my sessional, and I recognize that he probably doesn't have as much reputation as a prof might

Please and thank you for any tips/ calming words you might have ❤️ 

[M.L]

Did your reference submit your letter?