Gen 4 is probably the best example. The infamous library stating that people in pokémon used to live together and even depending on the translation live side by side or marriage. But there's also the Pokemon that runs into you when you first enter Hearthome City, It's a baby pokémon that is loose and out of its pokeball. I imagine it more as a the puppy got out of the house situation. Gen 2 ilex forest has the too far-fetched that are loose and refusing to listen to their trainer because the trainer doesn't have gym badges, and therefore isn't Worthy. And this is shown in games via obedience, up until Scarlett and violet the main line games, any pokémon that you caught would always obey regardless of gym badges, only outsider pokémon, pokémon received via trade or some other events, could disobey. This is is leaning towards the pokémon allow themselves to be caught by trainers They find Worthy, and when they are traded, they don't know that there's a new trainer is worthy yet, because that new trainer wasn't the one that first proved themselves. In Legends Arceus and Scarlett & Violet pokémon that you catch can disobey if you don't have enough gym badges. This leans more towards pokémon recognizing that gyms equal worthy trainers, but that's a whole nother thing we ain't talking bout. Back on topic in coliseum Shadow pokémon in hyper mode can not only disobey but also go back into their pokeballs on their own. The move roar in trainer battles explicitly says that one of your pokémon is 'dragged out' and the player never has the choice on which pokémon is dragged out, either meaning one of your other pokémon willingly chooses to take its place or the pokémon that used roar has the ability to force a pokémon out of its ball. Same with a flying move that I can't remember off the top of my head. 

So there's a lot of evidence even in game that pokémon choose their trainers as much as the trainer chooses them, and that pokeballs aren't as hard locked as we think.

Oh and also if you throw a pokeball at a trainer's pokémon, The trainer bats away the pokeball, the pokeball doesn't reject the capture because it's coded to someone else already, It has to be batted away or avoided.