This is a terrific congruent conflation of “missed the boat” and “dropped the ball”, both meaning to have made an error or mistake. Maybe the speaker was experiencing an earworm of that 1974 song “Rock the Boat” by the one hit wonder group Hues Corporation. In any event, this double whammy can be used to describe the mother of all mistakes. A big thanks to Marcia Riefer Johnston who sent this one in and is a new malaphor follower. By the way, she has a great website, http://writing.rocks. Check it out!
The speaker was referring to someone who had missed a big opportunity. This is a congruent conflation of “missed the boat” and “blew his chance”, both meaning to miss an opportunity. For some reason, “flew the coop” also comes to mind because of the rhyming of “flew” and “blew”. Nothing else comes to mind. A big shout out to Naomi David for sending this one in!