I recall a story from World War II about an American soldier who found a German cigarette butt near a combat zone; a seemingly meaningless find except the American intelligence officers knew that wasn't just any cigarette but instead was one used exclusively by a certain SS unit.
That story came to mind recently while reading an email. One small bit of information, mentioned as an aside, was combined with three other items that had been received from three other people to produce a very interesting and important piece of information.
Projects need information clearinghouses. Usually that is only one person but if diligent that individual can achieve a sense of what is known and not known.