How to discuss possible theft with house cleaner?

I have had the same house cleaner every two weeks for close to 20 years with no issues. He is very honest. The main guy comes every time and I trust him enough to have a key to my house, but his crew of 2 or 3 that accompanies him seems to change. On Sunday night I wore a diamond pendant and 3 not-valuable stacking rings. I recall removing them and placing them in the drawer where they live when I'm not wearing them. The cleaning people came Wednesday. I went to wear them again today (Friday) and found the necklace and one of the three stacking rings missing. I tore the drawer apart and they are not there. There is much more valuable jewelry in there that was not taken. I live alone and no one else has been in the house.

I'm heartsick about the pendant. It's not about the monetary value. My mother gave it to me on my 18th birthday and I lost her 3 years ago. I might be able to get behind the unlikely idea that I misplaced the necklace somehow if not for the missing stacking ring that has never left the drawer without the other two rings, which are still in the drawer.

How do I bring this up with my house cleaner - what do I say? Theft is a serious accusation, but not having seen anyone take my things I don't have proof, just a logical guess. While I don't expect to get my jewelry back, I feel he needs to know someone on his team may have stolen from me.

FYI, I am moving my remaining jewelry to a safe (kicking myself for not doing it sooner). Do I fire him? Or is there a reasonable response he could give that would take firing off the table?