Should he be able to sue- I think 'yes' should he sue? I think 'no'.
Does anyone really think the boat/shop/DM haven't changed or aren't paying more attention to head count now? This is about cashing in on a crappy mistake.
The important lesson we all should take away is how we treat the 'roll call'. Its sooo simple when the DM is conducting a count,
A) shut up-
B)stop moving around the boat
C)Don't answer for anyone else if you hear your name twice, clarify you are 'John Doe' and that you did or didn't answer previously
>>if you decide to go below and nap talk to the DM ahead of time, AND realize that you still might get rousted
>>if you are doing something outside of the normal dive plans, speak with the DM ahead of time. (long shallow dives/going back in to snorkel/ "check the anchor line" etc etc
Clearly whatever system was in place failed- no system will ever be foolproof (fools are too smart)
One of the easiest ways divers can avoid being left is to treat the roll call with respect, and understand- the best way to help out are the things above, NOT answering "Yeah, John Doe is back, he went below...." even if that is exactly what happened.