There's a simple explanation that only just occurred to me. Picard knows that a Starfleet vessel is not the safest place to keep a priceless archaeological treasure, what with all the attacks and dangerous space thingies. So he kept the actual naiksos in a private storage facility back on Earth or somewhere, and kept a replica of it in his ready room for display purposes. Only the replica was destroyed, and he had no reason to be too upset about it, because the real one was still safe.
Yep, this is just another example of us the fans trying to rationalize something in Generations that makes no sense. For this particular point, I'd agree with Christopher. If someone gave me a priceless, extremely breakable antique, I wouldn't be flying around with it in a ship that's constantly getting into dangerous situations. Especially in an age where technology can create an exact replica of said item. I prefer to think that after a few days Picard gave the original to a museum after replicating it. That's really the only reason that makes sense based on what we see.
It's actually not uncommon. There are many museums and art galleries that display replicas of famous works, rather than the originals, because of fears for the age etc of the real artifacts. Usually they do have a sign nearby telling visitors this is the case, though.
I can totally buy the idea that Picard wouldn't keep the original on-board ship, given how dangerous it is (as Generations aptly demonstrates

That's an annoyance with show-turned-movie. There's almost always an associative memory loss in the films, even if produced by the same people as the show. I was actually amazed that they remembered that Picard had a brother and a nephew!
It's especially weird because you just know had this pottery figure turned up later in the series, it would've been lavishly and lovingly explained, if only briefly.
I wouldn't want slavish attention paid to such things in the movies, mind you.
By contrast, the Mintakan tapestry from Season 3's "Who Watches The Watchers?" appears in both First Contact and Insurrection as set dressing in the ready room, which was a nice little nod to the fans.
Whether *that* is also a replica...
