The crazy thing about this play was, that as the video that AtomicDawg posted shows, that it was called DPI right away. Then the officials conferred and picked up the flag. They didn't "miss" it. They called it, then changed their minds.
We saw something similar in the Saints game 2 weeks ago, when the officials initially threw a flag for OPI, but then discussed it and determined it was legal because the contact took place with 1 yard of the LOS. I'm not aware of any exception to the DPI rule where you can wrap both arms around a receiver 20 yards down field.