hi mate,
i have a strong feeling, that the dealer you brought your car off, had another key, and then they used it to move the car outta the car park, and then they broke the ignition barrel to make it look like a theft. maybe post a pic up of the rims they put on, and keep an eye out for parts that were taken. make sure that you do not name the brand of the alarm on here becasue we are not the only ones who look at this forum.