As I understand it the laws against unreasonable search do not apply to non-law enforcement people on private property and your options in a case like this are fairly limited. You did have the right to refuse to turn out your pockets, but then they would have been within their rights to fire you on the spot.

Personally, I would not want to work at any job where they treated me like you were treated. Fortunately I work at a place that does not treat their employees like criminals and my boss is great to work for. I am not getting rich here, but I love what I do and look forward to going to work each day. I have been working here for 27 years thus far and I am still having a ball. I hope you can find a job that will be just as good for you.