After you have left, someone comes around with special celebratory T-shirts that everyone is expected to wear to work the next day.
Morning comes and, oblivious to the dress-code expectations, you get dressed in other attire.
Almost everyone else arrives at work in the special T-shirts.
An office administrator/friend volunteers to get you a shirt but your size is no longer available.
Someone within earshot refers to those few not wearing the T-shirts as “haters.”