They must have been the last to touch it. But no matter which team touched it before it went out of bounds, we'd get the ball at that spot.
ARTICLE 3. FREE KICK OUT OF BOUNDS. The kicking team may not kick the ball out of bounds or be the last to touch the
ball before it goes out of bounds between the goal lines. If the receiving team is the last to touch the ball before it goes out of
bounds, the receiving team puts the ball in play at the inbounds spot.
Penalty: For a kickoff out of bounds: The receiving team may elect to take possession of the ball 25 yards from the
spot of the kick or at the out-of-bounds spot.