Certain blocks seem to be disapearing occasionally.

I live in a desert and occasionally there are specific sand blocks that keep disappearing. And its not endermen that take them. I saw one sand block with a sugar cane on it disappear right in front of me. (So far it seems to be only sand blocks that have done this) Now I should point out that the last time this happened was in an earlier snapshot so I'm not sure if this is already patched up because I didn't find any reports about this bug anywhere.