Here's a list of ridiculousness:
-- NO ONE BOTHERS TO COMMUNICATE effectively:
...The bad guy could've just called the airport about his lost bag like she did and he'd have gotten it back without issue (instead of calling her directly pretending to be an aggressive TSA agent).
...Or when the mother is concerned that someone's been in her room and the ex-husband asks her what is she not telling him, she makes no mention what-so-ever about the luggage mix-up along with the aggressive unknown phone call inquiring about the bag in her possession.
...Or once the mother learned that the airport had already recovered the bag, she could have either gone to retrieve it again or inform the bad guy of where it was to go get it himself and leave her daughter alone.
...Or why did the bad guy even bother to kidnap the daughter and kill the dad in the first place? He could've just confronted the mother directly once he learned who she was and where she was staying. Had he done that he would've learned that first night that the bag was just downstairs at the front desk.
-- THE INCOMPETENT COPS:
...Who immediately dismiss the mother's story because they received a phone call from someone claiming to be her ex-husband just HOURS EARLIER... yet somehow, upon learning that her ex-husband has actually been dead since last night (so there's no way that was him who made that call) the cops now suspect HER of his murder?!
...What about the phone call they received "ONLY HOURS AGO" from someone claiming to be the dead ex-husband? They're not suspicious about whoever that was posing as her dead ex? Or why? No suspicions, at all, to the imposter's motives for calling ahead only to tell them not to believe anything his ex-wife might say?
-- THE SCAVENGER HUNT around town:
...What was the point? And when did he set all that up? Didn't he just fly into town the night before like she did?
...There's $50 Million in that bag... wouldn't getting it back ASAP be his only concern? Not whether or not she arrives at some random destination at some arbitrary time (lest he kill her daughter which would only ensure he'd never get his $50 Million back). Who knows what could happen to the bag while he has her running around town like a nut?
...It's also really convenient how she could always just happen upon the secret phones hidden at these huge locations (like the Museum and an Aquarium) within a city she is probably unfamiliar with.
-- ULTIMATELY:
Everything that happened happens only so the movie can happen to happen.