Can't see that this has been posted previously, but picked up from another forum:
There is a scam going around where someone puts a small scratch on your car, then leaves a note under the windscreen wiper. The note apologises for the scratch, and advises you that they have arranged for a mobile scratch repair guy to come round to your house or work at your convenience to rectify the damage. They will of course, pay for the repairs. You ring the mobile guy (number provided on the note), and he comes round to your house. He plugs a laptop into the car's diagnostic socket " to get the paint code ". He then tells you that he doesn't have that particular colour in his van, and will ring you when he's got it. What he's ACTUALLY doing is accessing the key or transponder information from your car. He will then get a key made up, and your car is gone! Obviously, all phone numbers are un-registered pay as you go's.