One of the last remaining rules that slows down play and makes no sense is, You cannot put a provisional ball into play if you believe your ball is in a penalty area.
The WA along with most tournaments always say, USGA rules apply. The USGA does not allow for drop areas, it does allow for any course / club to set a “local rule” that could include drop areas. Those drop areas should be included in a “local rules sheet”. If you play in a tournament where no “local rules sheet” is handed out, it always pays to ask the course pro, if there are any local rules in play for the event you are playing in.
The course owes you an apology for providing poor (or omitting) information, however once you have played a shot, that ball is in play no matter what. You cannot go back and identify a rule that “WOULD HAVE” benefited you if you would have known about it.