It seems like this has come up a few times now: for schools whose academic year begins before a certain date (maybe August 1st, I don't know), the date to choose their school is April 15th instead of May 15th. Being that we (UACOM-Phoenix) begins mid-July, we are one of those schools.
I know this process has been incredibly taxing on all of you, but hang in there. I absolutely love this school (and med school in general) and I'm so glad I stuck it out when times got tough. It's totally worth it in the end, if you really want to be a doctor.
Also, for those of you applying again in the future: I spent the day at the NAU Career Fair the other day with Admissions, and the subject of the Letter of Intent came up. Apparently (and I wish I had known this when I applied), keeping in contact with your top choice school(s) is definitely important and these LOIs are very helpful! Schools want to choose the students who will matriculate, so if you make it known that you absolutely plan to if accepted, you will look so much better to them! Update them, send thank-you notes, etc. - Show them the love!
Good luck to you all.