Blocks are throwing themself through walls

I was playing on a Survival Multi-Player (SMP) and when I was trying to mine some iron, I couldn't find it when it broke... turns out it was 6 blocks away from me. Now, I don't know if anyone else had this happen, but I just think it's kind of stupidly funny. And no, this isn't a joke report. Also, there was not a plug-in that made it do that.