[kentbrookug]

Not absolutely sure but I'll take a shot at it.
Since it went OB, you go back to the position it was last played. To me that means you place the ball very similarly to the same position and lie that was last played, even if it is in the hazard. You can drop the ball with your playing partner or rules official agreeing on the point of the drop. At that point, you have the choice to play it again as it lies within the hazard or taking relief according to the rules and accepting the one stroke penalty.

20-5. Making Next Stroke from Where Previous Stroke Made

When a player elects or is required to make his next stroke from where
a previous stroke was made,
he must proceed as follows:
(a) On the Teeing Ground: The ball to be played
must be played from within the teeing
ground. It may be played from anywhere within the teeing
ground and may be teed.
(b) Through the Green: The ball to be played
must be dropped and when dropped must first strike a part of the coursethrough the
green.
(c) In a Hazard: The ball to be played must be
dropped and when dropped must first strike a part of the course in the
hazard.
(d) On the Putting Green: The ball to be played
must be placed on the putting
green.