I'm somewhat torn on this one, as I wouldn't actually expect the TSA to be handling weapons and evaluating them, but at the same time I have to think that the xray image of a silhouette of a grenade and a real one would be different, making it an exercise in futility.
Grenades have a rather distinctive shape. It's beyond our pay grade to determine whether said object (which is likely to be a distinctively-shaped black blob on our X-ray) contains a live charge. TSA has other, much more highly-paid, people for that!
Scuttlebutt* at the airport is that the grenade was found in the bags of a honeymooning couple and was placed there unbeknownst to them by the bride's brother. Some prank!
* I have no idea if this actually is true