Previous experience of this in our club is that you should get a new frame. The only real way of telling is a mixture of xrays and ultrasound and even that is not perfect. If the drivers insurance company are informed then they should replace it – otherwise they can be liable if it falls apart when you are riding!
Watch out for the insurance assessors though – one of our guys got rear ended by a taxi and they sent out someone to inspect the bike. Normally looks at cars, no idea about bikes, never inspected carbon fibre, no knowledge of the material……. yet he is their expert opinion!