There are a LOT of people who could be in his ear telling him that rule. The fact that nobody got in his ear and told "this game is unwinnable" when the Ravens staff knew it is the reason he should be fired. It is his job to know the rule or to be around people who can tell him the rules. That failure means that they are now likely to be without both their all pro WRs, with Godwin almost certainly out for the year and parts of next year. That is gross incompetence and I would fire him for it.
Even if none of them knew the rule, the fact that Lamar and Henry were sat on the bench should have told them something was up