Get a lawyer and have a letter sent. Indicate you intend to press charges against the ASPCA for theft (given that they knew the cat was already owned and were surreptitiously trying to change the chip. Indicate that you also intend to go after the new family for receiving stolen property.

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I don't know if you can actually do any of that, but receiving the letter on lawyer's letterhead may scare them enough into moving heaven and earth to avoid having to find out.