Ball identified but not retrievable.

[Colin L]

Presumably he means as a rules official and I'd argue that he has a case. A marking should be used.

Rule 6-5 is clear and easy to follow.

Agreed - a marking should be used because 6-5 is clear, the player should put an identification mark on his ball. But that is a recommendation not a requirement.

There is no case to disallow a player from identifying his ball by manufacturer's name, ball type and number: Decision 12-2/1 is also clear and easy to follow.
http://www.usga.org/rules/rules-and-decisions.html#!decision-12,d12-2-1