I'm not sure what kind of response can be given here other than "not that I know of." It's hard to produce evidence that nothing historically significant has ever been discovered in the course of filming a history channel show (who has time to sift through every show they've ever broadcast?), but certainly I don't know of it ever happening, and I can say with a reasonable amount of certainty that it's very unlikely.

Why? Because TV shows are a form of entertainment, not a form of research - even in the shows that are portrayed as finding "new" evidence or conducting "new" investigations, if you watch carefully you'll notice that these are always structured around interviews/tag-alongs with an actual researcher who is doing their own investigations. And by the time these people have done enough of their "research" to come to the attention of history channel producers (I use quotes there because a lot of the people on these shows tend to be fringe/crackpot researchers by the standards of the field), any of discoveries that they're going to make have very likely already been made. That's why they're on TV in the first place.

TV producers are good at making it look like you might be watching new information/discoveries coming to light before your eyes, but this is very rarely the case. Real, professional scholars are exceedingly unlikely to want a history channel TV crew follow them around on the off chance they'll discover something interesting - being on tv is just not generally a goal that serious researchers have. And the people who do end up on camera and build their activities up as potentially paradigm-shifting/revolutionary are usually just re-treading ground that other scholars have already gone over, but with a "new" (and likely crackpot) perspective, or following a "lead" which other scholars have long ago concluded was a dead end.

One final point: real discoveries tend to be the product of years worth of painstaking research. They just don't make good TV, and as a result they're very unlikely to be filmed for one of these shows.

I believe there was a piece on the post war escape of Nazis titled Odessa File: Rise of the fourth Reich, in which the documentary crew investigated and came across some strong evidence to support a historical conspiracy theory that Martin Bormann had escaped Berlin in 1945, fled to Paraguay, died and was buried there, and then had his remains moved back to Berlin (presumably to protect Stroessner's government from embarrassment). More specifically they found a grave identified as Bormann's by some Paraguayan documents where a body had been removed with some rather expensive archeological equipment the history channel was able to provide.