re: So how about that trick play?

The ball crossing the line resulted in the downfield penalty because the linemen released past the line, which was probably the design of the play. As for throwing away behind the line, that isn't necessarily an automatic grounding penalty, but throwing in the neighborhood of the receiver is risky, and the ref may still misread it and flag you. On a busted screen pass, the QB will just drill the ball into the ground at the RB or WRs feet. That's a lot more difficult to do going across the field. Taking the 5 and playing the next down was just the safest bet.