If you want information on my encounter, here goes.
I was just walking back to my house after a long day of mining. I reached my house and went inside. I went down to my little "Pool and Storage" area that I built. Not big, but still, I did it anyway. I wanted to store the lucky diamonds I found. Before I got to the chest though, I heard my piston door open. I quickly went out of the storage room and tried to find out what the heck that sound was. I looked out my window, and I saw what looked like a person standing on my life-sized sand castle. I quickly went outside, but when I reached it, it was just a mess on the ground. Someone griefed my sandcastle. But, wait. I was in singleplayer. I checked the menu to see if it said "Disconnect." It didn't. It said the usual "Save and Quit to title."
Shocked, I decided to go for a boat ride to my second house and portal. When I got there, though, the portal was gone. There was just a hole in the wall. Then I looked behind me..
Herobrine stared back.