Is the data of Pokémon stored somewhere when traded away?

Question

I wanted to keep my starter from when I first played Pokémon with me, so I traded them forward, from Platinum to Soulsilver. One day however, I would lose my copy of Soulsilver and all my Pokémon from Sinnoh. While this is a total Longshot, is it possible that an instance of the Pokémon traded away exist somewhere in the data of my copy of Platinum? I never had the heart to get rid of my old save file. Should I cut my losses and move on? Or is there a chance I can get my Pokémon back?

Comments

While not an answer, my knowledge of coding would suggest that there isn't a direct trace of the Pokémon you traded away in the code of the game- it would be incredibly inefficient and cause the game to crash from memory leak if it continuously store every instance of a Pokémon that had existed in your savefile in the code somewhere (hell, My Soul Silver lags and is slow to save after years of saving the game and tons of full boxes of Pokémon). Your starter specifically would only have traces that it existed in what Pokémon your Rival choose as their starter, and stuff like Hall of Fame registration, but those don't store the Pokémon's complete data as far as I'm aware.

The only possible way you could get your starter back would be if you last time you saved before your current save had the starter on it, in which case some games save that file as a backup for if your current one gets corrupted; in which case, you could corrupt your current savefile to get it back. That, however, is incredibly unlikely from what you've revealed thus far.

Answer 1

No, Gen 4 games don't commit anything to the save file about Pokemon traded away (except the full struct for the Pokemon deposited to the GTS, if any, and assuming you count that as a traded Pokemon to begin with).

However, assuming you beat the Pokemon League with some of the Pokemon you want to retrieve, you may still be in luck. Gen 4 does store non-trivial information about each entrant to the Hall of Fame, which you can easily verify with your own game. The data stored for each entrant includes:

1. its species, level, nickname, gender, shininess, and original trainer's name, all in plain sight;
2. its moves (visible in D/P/Pt if you press A);
3. its PID (what?), as the game needs that to determine the Pokemon's gender; and
4. its original trainer's TID/SID, as this (plus the PID) is required for the game to know if the Pokemon is shiny.

Even better is you also get the Pokemon's ability, nature, size, and Pokeathlon stats, because those are determined by its PID.

What's missing is anything not listed above that isn't determined by the PID. This includes data like IVs, EVs, friendship, encounter details, Poke Ball, ribbons, held item, and bonus PP. If you know a bit about how the game's RNG works (introduction to the subject), you could also use the PID to find what its IVs legally could have been, except in the case of egg Pokemon.

If this is enough incentive to see you trek down the path of recovering your Pokemon (and making up some data to fill in the gaps), then the rough process for achieving that would be:

1. Dumping your save file. The easiest way to do this is with a hacked 3DS running a save file manager, which will write to an SD card.
2. Using this tool to load your save file's Hall of Fame data and extract the partial Pokemon data files. (Disclaimer: I have not used this tool.)
3. Opening your save file in PKHeX, importing the Pokemon data files extracted from the above, and exporting the modified save. If your Pokemon are Method 1 encounters (which includes all wild encounters and your starter), then PKHeX will know they're illegal from their IVs and encounter details. As above, you can deal with this by writing in plausible data with PKHeX, which may include looking up the Pokemon's PID in an RNG tool to find what the IVs should be.
4. Use your hacked 3DS to write the modified save back onto the cartridge.

So, clearly there is a barrier to entry here and several limitations. But you can indeed do something to bring your Pokemon back, assuming you did take your starter, etc. through the Pokemon League.

Comments

IT WORKED! I got my Empoleon, Rotom, Shaymin, legendaries back! I even lucked out and got my Japanese Ponyta that my friend gave me way back when I was 9! Thank you so much!

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Congrats man, that's just awesome. Don't suppose you need to be told, but now's a good time to keep a backup of that save somewhere safe!