Okay, a couple things: first, the ref was at the top of the three point line extended, so that puts him about 25 feet away, not 45
, no offense intended to anyone. In the three man rotation, that's roughly where he's supposed to be in that situation, because he was "middle away" when the play began. Lead and trail were both ball side as the play began, also right where they're supposed to be. The problem came as the player with the ball drove into the lane along the baseline, and crossed the face of lead as he did. NBD, happens all the time. Lead's primary responsibility there is to "stay with the players" (with his eyes) in the lane after the dish to the corner. The territory between the lane and sideline in that situation is middle's primary, anyway. It's a gap that will always occur on that play, because if lead mirrors the ball there (comes across the lane even with the ball) he'll be too close to the play to see a foul, should one occur. Remember the basket support is only a few feet off the baseline. It's a tough call because that corner will always be "uncovered" in that type of play.
Part of me wonders if perhaps the ref was reluctant to put SU on the free throw line with 12 seconds left under the "gotta be blood" principle, and making the out of bounds call was the way to avoid doing that. And I'm sure that came out in the post-game. Yes, it was potentially a game-changing mistake, but it didn't cost us. I wonder what would have happened if Lydon had fouled the shooter (he clearly got ball first, and the ensuing contact was minimal).