Thrown Tridents are disappearing after a short amount of time.

In my friends realm we have a Creeper Farm. And it has a Trident Killer in it. I have realized that after a short amount of time the Tridents just disappeared. And the pistons just kept pushing the creepers around. Then I had to look for more. There's a very slim chance that someone is trolling. But they'll be blown up for sure. And i didn't see any death messages. If its a bug please fix it.