^^ Another quick answer:

If I understand you right, Ben, you might have just been dreaming you were lucid, which I believe can happen.

The general feel of lucidity, I think, is one of feeling like your waking-life consciousness -- aka, You -- is present in a dream, and you have that "Ah-ha!" moment where you think or even say something like "Hey! This is a dream!" during the dream.

So if you didn't get that feeling of presence in the dream, and simply remember that you were lucid (especially if that memory is one of feeling like you were being told you were lucid, or being made lucid), then you may not have been lucid.

When you are lucid, BTW, and you will be, there will be no doubt!