It has come under some attention when playing in tournaments how
to score when a ball is lost or out of bounds and there is a need to not
slow the speed of play by going back to the spot from where the ball
was originally struck. Here are the USGA rules for this:
27-1. Stroke
and Distance; Ball Out of Bounds; Ball Not Found Within Five Minutes
a. Proceeding Under Stroke and Distance
At any
time, a player may, under penalty of one stroke,
play a ball as nearly as possible at the spot from which the original
ball was last played (see Rule 20-5),
i.e., proceed under penalty of stroke and distance.
Except
as otherwise provided in the Rules,
if a player makes a stroke
at a ball from the spot at which the original ball was last played, he
is deemed to have proceeded under penalty of
stroke and distance.
b. Ball Out of Bounds
If a
ball is out
of bounds, the player must play a ball, under
penalty of one stroke, as nearly as possible at the spot from
which the original ball was last played (see Rule 20-5).
c. Ball Not Found Within Five Minutes
If a
ball is lost
as a result of not being found or identified as his by the player
within five minutes after the player's Side
or his or their caddies
have begun to search for it, the player must play a ball, under penalty of one stroke, as nearly as
possible at the spot from which the original ball was last played (see
Rule 20-5).