I am a theatre manager and have worked in the industry for over twenty years, so this is in my wheelhouse. Personally I will not allow something of that size in my location. I cant speak for all of the industry or even my company policy. If the patron does not have a vehicle to return it to or doesn't feel comfortable leaving it in their vehicle, I will store the bag in my office. If the patron refuses my request, they're asked to leave. It's my belief that a bag of the size you're describing offers too many safety concerns. The first in everyone's mind is a firearm thanks to the nut job in Colorado. In my mind though I think of other issues, other patrons being inconvenienced trying to move through aisles. An obstacle to overcome if we had to evacuate the building due to an emergency, fire, tornado, etc. I could go on and on.
I commend you for bringing it to a managers attention. Often times we are behind the scenes taking care of other tasks and staff members are unwilling or bullied by patrons into allowing such an occurrence. Patrons have an inherent " I am right, you're wrong" persona in today's world. Threats of taking business and their dollar somewhere else. Unfortunately too many managers bow down to a patron when it's not warranted. If in my mind, I believe that there is any threat to any of my other patrons, you're asked to leave. If not willingly, then by law enforcement. The safety of others is not worth that customers money, period.
All in all, I believe you were correct and I would have thanked you for observation. I'd have comped your tickets and you would have been able to return at your convenience.
Bill - Returning after 15yr. hiatus
Yonex Vcore 100s, Super Tour 850@56lbs