More accurately, Mike Wolfe of the aforementioned series made a glorified cameo as himself, coincidentally coming into possession of a Viking war club that was also a murder weapon in 16-year-old cold case.
Unfortunately, "One Man's Trash" came off mostly predictable and unengrossing, though it did introduce an entertaining new character in the form of Ducky's graduate assistant Kasie (Diona Reasonover).
I'm completely willing to overlook the original coincidence that started the episode, that Gibbs and Ducky just happened to be watching an episode of American Pickers that featured a weapon they both instantly remember from a cold case we never heard about sixteen (!) years ago.
(On a side note, given that we're in Season 15, that would place this case about a year and a half before the series began,