I'm not sure that your dream quite counts as lucid. Although you said "this is a dream" your actions were more like you weren't truly aware that you were in a dream, just that you couldn't meet celebs because you were in one. You were certainly close.
I think the clear indicator (at least for me) is when you do an RC to confirm that you are in a dream. You can do an RC automatically before actually becoming lucid, and the few times that has happened to me I have then become lucid. Most times I already know I'm lucid, and then remember to do an RC later.
There is a hazy state of semi-lucidity where you don't quite get lucid (happens to me lots!). If you've never quite got lucid before, you will definitely know when you are lucid!
If you are not sure then you probably weren't, but don't despair. Just try to remember to do an RC.