One possible answer to the problem:
I had a similar problem when I found a grave listed for a friend's family member who had died as a child. It is a small cemetery in Pennsylvania which has not been used since about 1945 and is under restoration - Har Hasetim in Gladwyne Pennsylvania. The deceased was listed on the original cemetery list but the stone could not be found. My friend then remembered that the body had probably been exhumed and moved to another cemetery in a nearby town which the family used later.
Avivah R. Z. Pinski near Philadelphia, USA Researching: Zuchman in Sarnaki, Karczew, and Warsaw Poland Rubinsztejn in Sarnaki, Poland Reznik in Drohiczyn, Siemiatische, Poland
Avivah R. Z. Pinski , near Philadelphia, USA