On the morning of Jan. 19, 2016, University of Mississippi football coach Hugh Freeze tweeted a quote: “Look not back on yesterday—so full of failure & regret; Look ahead & seek God’s way—all sin confessed u must forget.”

Later that day, the coach flew to Tampa, Fla., as part of a recruiting trip using the school plane, according to documents reviewed by The Wall Street Journal. A few hours after the plane touched down at 5:30 p.m. in Tampa, his school phone registered a call to a number linked to a female escort service...