So when I did my mental 'snapshot' of the line, I saw three people that could be ruled linemen - snapper, LG, LT. So I had the LT as a back using blade of grass. But when the closest back scooted up, mentally I checked again, and I thought that the he, the snapper, and RG were on, and maybe I had just not waited long enough to see who was supposed to be where.
I think more than anything this was a play where the movement was poorly executed.