I have always figured it like for example IKEA furniture. If you have all the pieces of a chair in front of you, you do have a chair, it just needs to be assembled. However if 16 guys break into your house, beat you up and each one steals a few pieces of said chair, you no longer have a chair. Neither do any of the individual people who broke in. One has a chair leg, another has the seat etc.
So unless large chunks of a Shard are separated from each other, i would consider the shard still exists, it just isn't intact. If a lot of people pick up the pieces and move away from the bulk of the shattered investiture, the shard would stop existing (though possible to still reunite).