You should really contact them and ask them to check out your app status. Just call. Last year I applied to a school with a very lengthy period of sending out acceptances, and by late-April I still had not heard back, so I kept my hopes up and thought that maybe they were preparing the last batch of acceptances or wait-lists (this was at a Canadian school though, so diff application deadlines and ppl really start to hear back at the beginning of April). Then I finally worked up the nerve to call them one day, and it turns out, the rejection letter had been lost in the mail. They told me my results right away.
That is not to say this is the case for you, because it could be that your file indeed got lost somewhere and maybe it was an acceptance. So just call and get rid of your worries. Good luck!