How Could Refs Miss Pass Interference Call on Rob Gronkowski vs Ravens?

The New England Patriots came out of halftime of Saturday's divisional game against the Baltimore Ravens with a touchdown deficit. The offense was on the field with an opportunity to draw even at 21 and gain momentum for the second half.

Unfortunately, New England's first drive of the half stalled early when tight end Rob Gronkowski couldn't haul in a third-down pass from quarterback Tom Brady.

Baltimore took over after the ensuing punt and drove down for a touchdown and a 14-point lead. 

The problem here is that New England's drive should not have ended after three plays. Ravens linebacker C.J. Mosley clearly interfered Gronkowski prior to the incompletion (vine courtesy of CBS Sports' Will Brinson), which should have resulted in a penalty and a Patriots first down.

While officials must be tempted to allow for a certain amount of contact against the physical Gronkowski, Mosley can be seen grabbing the tight end around the waist long before the ball reached the point of reception.

There are plenty of acceptable instances of officials making judgement calls, but this looks like a clear case of one that was missed. At least a penalty wasn't announced only to be waived off after the fact. 

Do you think it was pass interference? 

[NBC, Will Brinson]