Wow. That is a complex prototype there. I am yet to figure out how you assign random numbers to those cards hehehhe.
Maybe create the cards like this: (not necessarily a better way...just showing an alternative)
I once created a few actors on the screen in a grid like position and I used 2 repeat blocks to create 64 actors :
In a 4x4 grid you'd need 8 different card numbers, and you can populate the list with the numbers in a repeat block again (just add the numbers from 1 to 8 twice). After that simply shuffle the list and you have perfectly shuffled cards (stencyl has a shuffle function somewhere).
Then when you click on the screen, check if you actually clicked on an actor, and if you did, the actor's X and Y positions will correspond to the index of the list that stores the card number(so you can change the animation of the card to the correct number assigned to it).
The rest is easy...just hold the last dicovered card number, compare it with the new one after you click again, if they match kill them, if not continue.
All this could be done inside a single scene behavior without the use of those horrible ¨get something from some behavior¨ blocks (I'm yet to figure out how those work hehehhe).
P.S. You have a bug: Clicking on the same card a few times eventually kills that card and the whole game won´t work correctly.