Re: could this be the baby moving?
It's possible you felt your baby moving...you are getting to be around the time where you could begin to feel it. I think I started feeling strange, very occasional, and very light sensations that got me wondering around week 17. It was at week 19 at my doctor visit that in describing the pokes I was feeling, he assured me it probably was the baby moving. I didn't feel those "flutters" and "bubbles" most people talk about. Mine was more of a little tap here and there.
As for feeling it from the outside...I would doubt you felt your baby already. My doctor didn't even start poking around at me to feel the baby himself until around Week 19. My doctor showed me how I could press my stomach to feel the baby in there, but I'll tell you, it was very subtle and I had to press pretty deep, and work really had to find it. It was only a lump in there. The doctors cannot tell what body parts they are even feeling that early on.
If you felt something hard, it could have been nothing...you were just really wanting/hoping to feel something...or maybe your uterus tightened up a little and it was harder than normal for a minute or 2. The hardness really could have been anything.