Sorry, why is it harsh, that the retesting facility would disable a vessel deemed unsafe to hold high-pressure air? After all, is it not why they are subject to re-test in the first place, to ensure that they are safe? Or is it the fact that he has had to pay for the testing? Only ambulance chasing lawyers offer a no win no fee service.
Frankly, if he bought it out of test, and knew it was out of test, its a case of Caveat Emptor - buyer beware.
Yes we can feel sorry for him, but life is harsh, get over it and move on.