Ease of exploitation and ease of discovery have basically nothing to do with each other.
Relatedly, "many eyes makes all bugs shallow" is, and always has been, totally horsepuckey. (And despite it being horsepuckey, and horsepuckey which is trivially exploitable in that if you believe it you'll produce software which can get owned by people who are better at e.g. counting to four than you are, people still believe it to this day.)
Seems quite likely that someone would have discovered it sooner, especially since it's so simple to exploit.