Disappearing Blocks

Blocks have begun to disappear from my world. They have been disappearing in chunks (Unfortunately, I did not think to take screen captures before I repaired the damage). First, it was part of my house. I thought maybe it was an Enderman when I was off doing something. It was a specific part of the house. Then, my cow farm fences disappeared which has led me to believe that it was not Enderman. Is this a bug? If so, is there a way to troubleshoot?