Is there a way to determine if an airline flight actually happened?

My mom got caught in the big East Coast snowstorm. She was supposed to fly out west on Sunday, but was told over the phone on Saturday that her flight was cancelled (for Sunday), even though the online status did not show cancelled. The agent cancelled her Sunday ticket and put her on a Monday flight. So, my dad suspects “foul play” in that the airline bumped her back a day to accommodate the stranded flyers from Friday/Saturday. Is that possible or is he being paranoid? Can you tell if a specific flight on a specific day actually went off (I’m sure there’s a log, but don’t know if it’s publicly available)? Thanks.