The Washington Post has a profile of the historian at Arlington National Cemetery. The piece closes with this:

One time, he was making his way through the cemetery, when he spotted what he thought was a discarded soda can. How could anyone be so insensitive, he wondered.

But as he walked over to the headstone -- the grave of one of the casualties of the Persian Gulf War -- he realized it was an unopened can of Iron City Beer and that there was a note attached: "John, we said we'd share a beer when you came back. Welcome back." Sherlock left the can where he found it and walked away.