The player is responsible for the caddie's actions

The player is always responsible for any actions committed by his caddie during the stipulated round. I often have to intervene in explaining the basics rules of conduct to the caddies. These are a few warnings:

count the number of clubs in the bag
do not wear golf shoes
never stay behind your player when he is making a stroke
be careful not to step or move your player’s ball
make sure the player uses always the same type of ball
never drop and lose the ball in a water hazard or a cliff
do not drop any equipment on the ball
never touch other players bag unless asked.
etc

In many of our local professional tournaments, players use local caddies with little or no experience. I always try to explain to them how to avoid some mistakes.

On July 20th, 2017 at the Open, K.T. Kim’s caddie made a mistake that gave a one stroke penalty to the Kim.

Kim’s fellow competitor David Duval send his drive in heavy rough. He decided to play a provisional ball. When arriving at the area, Duval found his ball. He told the other players and caddies to pick up his provisional ball. Kim’s caddie picked up the ball and gave it to Duval. Duval told him it was not his ball. By mistake Kim’s caddie picked up the ball of his player.

This is a one stroke penalty to Kim and he had to replace or drop the ball. If the lie is known, the ball must be replaced. The caddie did not remember the lie!! or did not see it. The rules official had to conclude the player must drop the ball at the approximate spot. Kim ended up with a bad lie.  He made a triple bogey on that hole.