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Argh. The only copy of it I can find has the nickname "Spearmint." Do you still want it anyway? Although I probably should ask Omega if he still has a non-nicknamed one. I'll see if I have a savefile that can change its nickname.
He was in Celadon. The Latios was the correct one. I'm glad I found it. I'll now attempt to trade all of the pokés from the thread. They seem to be a lot rarer now than they used to be before.