Grave robbers, what to think, how to cope ?

We went to the cemetry today to pay our respects to my dad who ped away 3 years ago and when we got there a heavy ornament was missing. There are lighter ornaments still there that could maybe have blown away, but not this missing heavier one. I am distressed and words fail me. I can't believe it. We reported it to the cemetry warden, who will put it in a book for report as stolen, but really, | don't get it....What do you think, can you believe it ? My dad was a diamond, trust me....