Hi!
That's exciting I also received an email offer from York and am waiting on a letter with funding details etc. I'm pretty sure that's where I'll be heading in the fall as well.
I wouldn't give up hope - I finally heard from York today! And surprisingly the email was in my junk mail folder... be sure to check your junk mail as well! Since they gave you a date - I'd just wait it out until the end of the day tomorrow and if you still haven't heard anything, then send them a quick polite email.
I'm also waiting on York.... I did find a facebook post from the Education department regarding master's applications in case anyone else is waiting to hear back about that. "The Graduate Admissions is presently adjudicating the doctoral applicant files. Once they are complete, they will be adjudicating the Full-time MEd applicant files and decisions will most likely be made sometime in April." This was posted early March.