Lastnight I was having a dream that my friend had made a sign, and put it up in his yard. It was about 50 yards away, and he told me that it would make you lucid. So I AP, in the dream, and went to see the sign. I felt very excited, because now I knew a way to become lucid. Some co-workers came over, and looked at the sign, and became lucid allso. So I asked if I could make a sign, he told me that I had to place the sign somewhere a longway from my house, and by the time I would go look at it I would be lucid. Now I woke up, and thought I had, had a LD, but I really cant tell If it was, or if it was a false LD. It felt very vivid, and now Im actualy thinking of doing this… Placing a sign that says… “Is this a dream” about 50 yards away from where I live. Who knows, it might actualy work.
I would say that most often, if you are not really sure, then it wasn’t a LD. 
Dreams can be very vivid too, and you can remember everything as if you were there, but still, you may not have realized it is a dream. That is actually such a weird experience, different from everything else, I think it is quite improbable to confuse it with a FLD.
I think in a real LD, you may have questioned the whole concept (for once, you would not have needed a sign to become lucid since you already were 
).
A false LD maybe? 
But sounds like you had some good control over that astral projection. Congrats on your dream power control 
and about the sign thing: Wouldn’t hurt to give it a try seeing if that will help you become lucid in your dreams 
Good luck in your next dream!! 
and congrats on this particular dream of yours, I think it could potentially be a turning point for your dreaming 
if the sign thing works 