We reported to management we left a very expensive...

We reported to management we left a very expensive necklace in the room once we realized after checking out. They claim not to have found it when we know for a fact it was left by mistake in the room. It is very apparent housekeeping stole the necklace. We were told by head of house keeping they are not responsible for items left. This is an unacceptable answer. They employ dishonest staff. Very poor customer service