Mask of the Matriarch

I just had a question pop up, making me wonder about if I've been playing this card properly.

Does playing the Mask cause it's effect to go off?

I've always said no, because playing a card preceeds the effect and therefore the playing of the card is finished before the text comes into play, so no additional cards get played. But one of my players disagreed tonight.

My search-fu was weak, does anyone have a good answer?

I've always played it the way you do. It's effect can't go off until it's played making the mask an excellent target to Stratosphere.

Same here

The text would enter play at the same time as the card, so that when the text is active the mask is already in play.  So you did it right.

I guess this is the flip side of the Informant ruling, in a case where it helps the heroes.