It actually wasn't prevent defense at all. In a prevent, at least a safety would have been behind the receiver on both of those long touchdowns. Instead it was straight man to man where Walker got behind his man and the safety didn't react in time (he probably though Hollenbach was about to be sacked, since I did too), while the second was a beautiful out and up move by Melendez. I'm not exactly sure who got burned in each case (although I think the second was Goddard), but the out and up move was just executed so well that I really didn't blame the CB. When I saw it in live action I said "oh shit" before the ball was even thrown because I knew what was going to happen.
Obviously the Heels struggled on defense, both against the pass and especially against the run (I can't even count how many times Maryland ran a simple counter with great effectiveness, as it was like watching someone play Madden using the same play and the same formation), but they still could have and should have won the game. They had chances, they just didn't make the plays that they needed to, while Maryland did. All credit to the Terps.