They shouldn;t be able to get money from you, but there is a really stupid part of the Road Traffic Act that we have to abide to.
If your certificate of insurance has not been retruned to the insurer, and there is no other insurance in force on your vehicle, then if it is involve din an accident with the new owner, then technically your insurer may be liable due to the outstanding certificate - stupid I know. Not entitrely sure of the in's and out's as I don't work on liability, but that's the basics behind it.
However, you shouldn't be liable for this, and realistically, your insurer should pass this info on to the third party insurer and tell them to contact the new owner directly for any monies owing.
Same thing applies with stolen cars - if the thief is identitifed, then the insurer is held liable, and has to attempt to claim the money back from the thief. If the thief is unidentified, then there is no liability on the insurer under the road traffic act.
There are probably people out there who could explain it better (New Judge?) and hopefully set anything I've got wrong straight, but I'm pretty certain I'm on the ball here.