I don't think you we're lucid. This is complicated...
You might've known you're dreaming. But didn't just notice. Like, a class mate of mine says he has lucid dreams all the time when I brought the subject up. But he doesn't see anything so great about it, because he does not know what he could do, which is anything he could ever wish for...Uhh...This is really complicated...

If you're wondering why you remembered them so clearly, it's just because you woke up straight from the dream. And it could be that you sleep so that you normally wake up later after the REM cycle...If you could somehow trigger yourself to wake up straight from the dream you would propably remember them as clearly as you did that time.
I also have trouble remembering my dreams but I've gotten a lot better...(It used to be so that I didn't remember any dreams or even tiny parts. If you don't wake up straight from a dream it is still possible to remember the whole dream or just parts too though...Just try to focus on "What did I dream" for about 10 minutes or less, depends on person. Don't move that much either, or put lights on. That will most likely make the dream fade away completely...

I also find, if I don't remember any dreams no matter how hard I try, and I go back to sleep. I recall far more clearly.

Sorry if this is too long, I get carried away easily.