Thank you everyone, for your responses and for your words of support. This was the only program I had applied to - was selective as I already have a Masters degree in a different field from another leading university.
I was quick to share the short lived 'good news' with family, close friends and my recommendation providers. Everyone seems to be so surprised that a world class school could do this. I am unsure exactly what transpired - there was a nice personalized note at the bottom of the offer letter; so am inclined to think it was not a systems or a process error.
Will try inquiring after this admissions season is over. If it was because of any perceived deficiency in my application that they discovered after the initial decision - will try to address that and apply again. If they refuse to discuss or provide feedback, I will just accept it is not the place for me and move on. It surely is hurting now, but hopefully it will not after some time.
