Roll-Back?

I was on vacation for about a week, and I came back onto the server and half of my house is gone. I had a sheep farm with a wide variety of colors, and it was an addition to my house. May I ask why this is? Someone on the server told me it was a "roll-back" for when players do something wrong, but I have not done anything wrong to my knowledge. I have not griefed or stolen, and I do not have any hacks or mods. I would apprieciate it if this issue was fixed, and if this said "roll-back" could be undone. Because this is extremely inconvenient, and I happen to like this server alot, and I worked very hard on my house. Thank you, Shiney25