I don't see a reason for saying that the flaming sword and cherubim were symbolic either. They weren't allowed back in because they lost access to the Tree of Life which would have granted them immortality in their fallen state. Thus, they would have to be treated as the Fallen Angels who fell in their immortal state. Given the overall message of the Bible, this is evidently very real.
As far as Genesis 3:24 obstructing current man's ability to look back with the scientific method to see if the Genesis account actually happened, I don't think that's the case. According to Revelation, the Tree of Life is in heaven, not this realm. (Revelation 2:7) Waiting to be brought back to Earth along with New Jerusalem. (Revelation 21-22). This would indicate that the Garden of Eden of Genesis is no longer a location on Earth. Also, taking into account the flood, the Garden was destroyed along with the rest of the pre-flood geography. Either that, or it is the Paradise spoken about in Revelation 2:7 where the Tree of Life resides in heaven, not this realm.
I'd argue that the reason scientific research cannot access accurate information about the creation process is that science does not work that way. While I appreciate the things science have brought us, it is not the end all be all of finding truth and answers. It is but one process. Its elevation to the status it has today was done so by individuals who did not believe in God or the testimony of the Bible. However, I have found there are plenty of believers who utilize science to discover that the Bible is accurate in what it says about creation.