In Creative, when I extend a piston and then click on it, it drops a piston. However, it's Creative, after all. In Creative, blocks don't drop when you hit them.

How to Reproduce: (Pretty Easy)
1. Make sure you are in Creative.
2. Place a piston anywhere.
3. Use a lever or other mechanism to "open", or extend the piston to it's full extent.
4. Hit it.
5. It should drop a piston block.

This works with sticky pistons as well.

As can be seen in the screenshots, I have an extended piston, and only one piston in my inventory. When I hit it, I then have two pistons after picking the block up.