Yes, certainly. I disagree - wiki, at least, is a source and/or has sources. A game isn't a source and doesn't have sources - at least no sources that are publicly available. In this case, the manual doesn't even tell us what is intended by the Aurora plane in the game - so we don't even know if some random programmer who doesn't necessarily know anything we don't believes it to exists or not. The fact that it is in the game doesn't tell us anything about whether or not it exists.
Also, as do most people in this forum, I chose the wiki source because it is easy. However, it does include as a source, a book I have, "Skunk Works", which is a primary source by someone "in the know" at Lockheed (the director of Skunk Works) at the time the code name was accidentally released. If you like, I can type in the quote, but what I said in the first quote is a paraphrase of it. There is actually some interesting discussion of the issue - including a statement that the gov't did solicit Lockheed's help in developing such a plane and that Lockheed declined because they knew it wasn't possible.