"Clear by what you were wearing" and "coming from my office" aren't jiving for me. Were you in a tank top, skin-tight shirt, or was your waist somehow exposed? Otherwise it wouldn't be hard to conceal a weapon.

Detaining (arrest or other longer term) someone without probable cause is unconstitutional, but restraining them is allowed.

Sorry if I'm not helping you to feel better about your shitty experience, but that really is what I'm trying to do. If you step back and realize it was nothing personal, just business, you'll feel better about it. Like Ryllharu said, if you match a description black/white/otherwise, you're going to get the 3rd degree. It's all in the name of crime control and public safety.