June 2, 2015
When can I declare my ball as "lost?"
A ball can never "Be Declared Lost" - it simply is or isn't lost and your answer comes from the definitions section of the Rules of Golf for "Lost Ball".
A ball is deemed "lost" if:
a) It is not found or identified as his/hers by the player within 5 minutes after the player's shot or his/hers or their caddies have begun to search for it;
b) The player has made a stroke at a provisional ball from the place where the original ball is likely to be or from a point nearer the hole than that place (see Rule 27-2b);
c) The player has put another ball into play under penalty of stroke and distance according to Rule 26-1a, 27-1, or 28a;
d) The Player has put another ball into play because it is known or virtually certain that the ball, which has not been found, has been moved by an outside agency (see Rule 18-1), is in an obstruction (see Rule 24-3), is in an abnormal ground condition (see Rule 25-1c), or is in a water hazard (see Rule 26-1b or c);
e) The player has made a stroke at a substituted ball
If you have not done any of the above, you ball is still in play and not lost.
Happy golfing and remember the Rules Matter.