I got into a battle with a rare Tree Moss. I used a blue trap on him and it said that I succeeded and it was added to my stables. But he's not there. Nor is he in my hatchery. I'm actually not worried about it was going to give it away but thought I'd let you know.
It was arond 4:40 game time. Happened X:049 Y:013

In these situations, I always just assume that it ran away.

To always 100% verify the results of a trap, check the battle log after using it and it will tell you exactly what happened and if it succeeded, it will provide a link directly to your new pet's profile page. This way you can always verify that it worked and have proof for me to look at if it something broke.