Accidental touching under the net.

[FMadera]

The definition of a block involves reaching higher than the net, so treating this like a block and allowing a team to reset their hits is absolutely not an option.

NCAA is very explicit on this exact situation:

Rule 15.1.3.2: If the ball inadvertently contacts an opponent while part of the ball is in the plane below the net, the ball is out of play and it is not considered a fault by the opponent.

USAV Casebook Ruling
10.14 R2 (note: Receiving Team Player 2, not the second referee) is standing close to the net when S2 contacts the ball so that it hits R2 below the net before it completely crosses the vertical plane of the net.

Ruling: The ball is “out.” (Signal pointing under the net). Next service to Team R. If, in the judgment of the 1st referee, no player from Team S could have made a play on the ball before it passed under the net, there was no interference.
Reference: 10.1.3, 11.4.2