Removing a fob from Prius ECU

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Hello,

We just bought a used 2007 Prius, but it only came with one fob.

We are planning on buying another SmartKey fob and getting it programmed for our car, but I'm a little worried.

Based on a VIN check, it appears that the car was repossessed two years ago then the dealer got it through a dealer auction.

My worry is that if the original, disgruntled owner can track down the car they can steal it from us with no trouble whatsoever.

My question is: If a Toyota dealer is programming a new fob for the car ($140 from our local dealer - OUCH!), do you think it would be difficult (therefore, expensive) to have the missing fob deleted from the car's (ECU) memory?

I will be asking the dealer this question as well, but I'd like a sanity check from someone with no monetary stake in the outcome.

Thanks.

-- Paul