They must be hiding because he is a VP candidate!!
From the AP
He did not elaborate, but aides said it was mostly a reference to Biden's reputation for long-windedness and off-the-cuff remarks that sometimes backfired. He ended his 1988 presidential run amid allegations of plagiarism. As he began a 2007 run, he called Obama "articulate" and "clean." He also drew criticism for saying "you cannot go to a 7-Eleven or a Dunkin' Donuts unless you have a slight Indian accent."
If it was an off the cuff remarks why would he say it when he knew he was being recorded! I don't buy it.