Weird Lag?

So me and my friends opened up a small creative private server, which was bukkit with a few plugins. I was building my house when I noticed sand blocks and water, which I had built into, wasn't falling down into my house. I covered it up with one of the new blocks, andesite (not sure if that has anything to do with it) and then I heard a creeper noise and then the screen had the dirt pattern on it? I disconnected, reconnected and the house I built was gone :/

(Please do not say "fake" I want people who can help me and not call me out for an unusual story - thanks)