How long can a golfer look for a lost ball before the ball is considered officially "lost"?
Golf is a club-and-ball sport in which players use various clubs to hit balls into a series of holes on a course in as few strokes as possible. In golf, a "stroke" is any swing forward of a golf club by a golfer who is trying to strike the golf ball. Strokes are the means by which golfers advance the ball around the golf course, and each stroke is counted as part of keeping score.
Rule 27: Ball Lost or Out of Bounds; Provisional Ball (Rules of Golf). As of Jan. 1, 2019, a new version of the Rules of Golf went into effect.
27 (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.