The ghost Redstone block

I made a Redstone clock by placing a Redstone block in front of a sticky piston, then having a line of Redstone reaching from the block to the piston. Then I went offline. When I got back, I found my Redstone clock had stopped. When I looked into it, there was a ghost Redstone block. By that I mean this Redstone blocks texture was darker, and I could kind of interact with it.. I could stand on it and stuff, but when I tried to break it, I broke a block behind it instead. And when I tried to push it with a piston, it after as an immovable block. Help?