Admitted but not invited to Open House?!?

[jenix]

Alright fellas, I need your sage advice here. I have applied for an MS in an engineering field to this decent school (actually my 2nd choice of 4 programs total)

The problem is I didn't contact any faculty prior to submitting the application. So I got this email from the department that they would be willing to recommend me for admission if I would change my application from MS-thesis to MS-coursework only, since they would only admit students who already have faculty willing to supervise them. I did change my application

It's been about a month since and I am yet to receive any offer (official or unoffical) of admission. So I decided to call them today to know what's up: thus when I should expect any offer and when they would be sending out invitations to an Open House. It turned out they've already sent them out. And I didn't get one. Though I understand that I've not yet been offered admission (recommended by dept but the grad school makes the final decision), I wanted to know whether it's kinda unsual to get admitted but not invited for an Open House. Has this got to do with me being offered the course-work only MS?