Have you had an opportunity to review the employee manual? There may be clauses that prohibit weapons.
Additionally, keep in mind that Michigan is an 'at will' state. They can can you for no reason at all, any time. They may just be 'uncomfortable' with an armed employee, and decide the easiest course is to fire you.
I'm no longer surprised that people don't notice an openly carried 1911. Spent an hour talking to a potential boarder, walking around the property. She never even noticed.
I think people 'see' what the expect to 'see'. They expect to see a phone on your hip, so their brain interprets the object on your hip as a phone.
As once said on CSI- 'when you hear hoof beats, think horse, not zebra'; in this case, however, it WAS a zebra.......