Bozak was playing his first preseason game as a member of the Blues after signing with St. Louis on July 1.
Sammy Blais opened the scoring for the Blues less than six minutes into the opening period, scoring his first of the preseason.
Minnesota had carried a 2-1 lead into the third period on goals from Brennan Menell and Justin Kloos.
More than 14,000 fans attended Wednesday's preseason game, which was the first-ever NHL game in Des Moines.