There are items missing from my dead fathers belongings?

I have receipts and payment records for items that my father purchased and as I have been going through what his landlady gave me and things are not adding up. Whats weird is that all these items were in a safe that only she had access to. I am the ONLY other person that knew of the items of value as in the event of his ping I was to retrieve it (I am his sole heir). I also live 1839 miles away from his location and I have not been out there in quite some time. However, dad and I talked everyday, sometimes 2x's a day. He also told me literally 2 days before he died of the "routine" that should be followed in the event of his death. Grampa died early and dad has been preparing me for this for over 10 years. Now, I am seriously thinking that this woman has stolen from a dead man. I have record of the purchases. The items are collectible gold coins and some 24k Baht jewelry, about 60K worth. So, what do I do? It was her property and dad had no friends or family out there? Help?