[Powderman]

OK. First, you were on private property.
The owner of the property or their designated agent or caretaker sets the rules.
If your employer states that there are no firearms allowed on the property, then you violated the rules. You may not like it, but it is PRIVATE property.

What could have happened? Well, be thankful you still have a job. You could have been fired.

Or, you could have been excluded (trespassed) from the property. If you stayed or refused to leave, you open yourself to arrest for Criminal Trespass.

Sorry, bud--but the owner of the property sets the rules. If you don't like the rules, find another job that will allow you to carry on the property.