There is no legal obligation to report an accident to the police if you exchange details at the scene.
There is also nothing in the OP to suggest he was blasé about it - at the time it didn't appear that the OP was injured, he gave him his card and said to send him the bill for repairs to the bike. Really, what more do you expect him to do?
Actually, what you said about there being no legal obligation to report an accident to the police if you exchange details at the scene isn't strictly correct:
What must a driver involved in a traffic accident do
A driver involved in a traffic accident should stop whether or not the accident was their fault if:-
anyone, other than themselves, is injured; or
another vehicle, or someone else’s property, is damaged; or
an animal in another vehicle or running across the road is injured; or
a bollard, street lamp or other item of street furniture is damaged.
If you have to stop, you must remain near the vehicle long enough for anyone who is involved directly or indirectly in the accident to ask for details. This could be, for example, the owner of an injured animal, a relative of someone who is injured, or the police. The driver must then give their name and address, the name and address of the owner of the vehicle (if the driver is not the owner), and the registration number of the vehicle.
The driver may also have to report the accident to a police officer or at a police station, in person, as soon as practicable and in any case within 24 hours. This duty arises whenever the driver has not given their name and address at the scene of the accident, whether or not they were asked to do so.
If any personal injury is caused to another person, the driver must also produce a valid insurance certificate if asked to do so by a police officer, injured person, or anyone else directly or indirectly involved in the accident. If the insurance certificate is asked for, but not produced at the time, the accident must be reported to a police station as soon as practicable, or in any case within 24 hours, and the insurance certificate must be taken to a police station within seven days of the accident. However if the driver is asked at the time of the accident to produce insurance details and does so, there is no further obligation to report the accident to the police, as long as they have complied with the duties described above.
For more information about personal injuries, in England and Wales see Personal injuries, and in Scotland see Personal injuries.
In the case of a damage-only accident, the driver must give insurance details to anyone who may wish to make a claim against them.
In all accidents, drivers should inform their own insurance company.
For more information in England and Wales about making a claim to your insurance company, see Motor insurance in Consumer fact sheets.
http://www.adviceguide.org.uk/index...l/traffic_accidents.htm#what_must_a_driver_do