Rules of Golf - Lost Ball
Rules
You cannot Declare your ball last.

It's a common misconception that you can declare your ball lost, but the Rules of Golf don't allow this.

Indeed, the definitions section addresses this head-on, defining ‘lost’ as: “The status of the ball that is not found in three minutes after the player or their caddie (or the players partner or partners caddie) begin to search for it.

A ball does not become lost as a result of the player declaring it to be lost. So, if you hit your ball into a bad spot, turn to your fellow players and say “I'm declaring that one lost” that holds no water. Even if you don't want to look for it, your opponent or playing companions may still do so, and if they find it, or think that they found it, you can't just say “that ball is lost” and ignore it.

If you really don't want to risk finding your original ball, you can just play another under stroke and distance without declaring it a provisional. But beware - it automatically becomes the ball in play even if you find your original in the middle of the fairway after an unseen ricochet.