For a guide that takes you step by step on how to remove the SIM and microSD, I'm surprised they didn't mention the top part of this midframe (still attached, in the pictures). This top part of the midframe also needs to be removed before you can take out the motherboard.
You need to disconnect a ribbon not listed in these directions first, then pry that midframe up with the help of a guitar pick. This ribbon is located by the back-camera, next to the digitizer ribbon. This ribbon is connected to the midframe so it is essential you disconnect this before lifting the frame up.
The frame is really snapped in there so don't be afraid to use a little force - for reference, you will use more force to pull this frame off than you did to pull off the back-cover of the phone. Once this piece is off, your phone should look like the picture in step 14.
I did the same... Digitizer came up with my front glass. FOR THE UNAWARE (as I was), the digitizer is a rectangle panel that looks like glass and is very easy to accidentally pull up and crack (especially if you are wedging guitar picks and the like in there). The bottom right corner of the phone (where the Back button is located) is where the digitizer ribbon is located. The fat, yellow digitizer ribbon is actually UNDER the digitizer panel, and the black ribbon for the Menu & Back buttons is located between the digitizer panel and the front glass. You will not be able to use your phone if you break the digitizer or its ribbon so bear this in mind when removing the glass. :(