I've been a bit leary about posting anything on this, but I don't know if this is an intended thing or not and it's easier to decide with the opinions of others... (Admins - if you think this is one of those taboo things, feel free to delete/lock this topic)
If you're battling a pet and it's not the rarity that you're looking for, normally you would just concede and go look for another pet to battle (hoping that your luck will improve). But when you concede, the pet that you were battling despawns. This isn't good if the pet you're trying to capture takes a long time to respawn.
So instead of conceding, just log out. When you log back on, the pet will still be there and you can battle with it again (and hopefully you'll get the rarity you're looking for this time). There is a chance that someone else may be at the right place to get to it before you get back online, but that's the risk you take.
What do you guys think? Is this intended or is it a bug?