I cant comment on the issue you are having posting pictures. Maintenance is indeed vital part of an airline and the last thing that a carrier will cut/minimize of its service. I do believe that the ground crew was aware of the missing part you mentioned and was already noted. It may have not been a "vital" part that could have prevented the aircraft to fly, after all, you did make it to MCO in once piece and without any inconvenience, except for being nervous, correct? Planes, cars, trains, boats can operate safely even if they are missing certain parts. Most of them have safety features built into them as well as self diagnostic check lights and procedures. There are certain procedures that need to perform on an aircraft after so many hours of flight time, much like the car oil change, and the like. Some are more critical than others.

Have you seen those Jeep Cj's with the removable doors, it may not be normal but people do drive them. The flight attendant was correct when she mentioned that should have said something. There is a saying that goes "If you see something, say something". Maybe by alerting them they could have checked and verify the situation, perhaps an announcement could have been made to ease the passengers, who knows. You even could have opted of not flying as well. As for Frontier response, it appears to be a standard response and addressed the issue, they take safety seriously. I'm not sure what they meant regarding no being able match an issue to what you describe, seeing that with the flight # and date they can easily verify which plane flew the route and what service orders have been recorded, but perhaps they are not involved with that matter or the issue was minimal and solved without any notification.

Frontier is certainly responsible to this, after all they got you to your destination didn't they? Where you in danger, does not seem so. Security concern, well, more like maintenance, but still it appears maybe it was not vital enough to delay/stop the flight.