It's garter stitch. It has different colors. It's a scalene triangle. This one made my inner-geometry lover pretty happy :) When I showed the sketch to my daughter, she said it was very much 'my style' - whatever that is!
Obviously I can't show any photos what with it being a mystery and all, but here's the place holder on my pattern and project pages:
These are the colors I used at least!
You can find the pattern here - it's half price until April 4 when the first clue comes out!