Accused Of Shoplifting (more Like Entrapment)?

I went shopping with my wife today at QFC (Quality Food Center) where we were accused of shoplifting by store security (more like a separate security firm hired by the store). We went by a shelf of NIVEA cream for men and I was curious to the smell of the cream, not seeing any warning regarding breaking the wrap (foil wrap over the top after unscrewing the cap), I peeled a portion of the wrap off to smell the product. After that, I put the product back on the shelf after screwing the cap back on and went to shop other things.
After checking out at the self check-out and two steps after getting past the entrance, three security men blocked us off and accused us of theft. I admitted to peeling off a portion of the wrap and followed these men to the store office where they spent 1 hour filling out paper work. I offered to buyout the product and denied knowledge of that act being classified as theft (not seeing any warning regarding voiding of the product without wrap since there are other facial cremes without wrap/foil period), but they wouldn’t allow me to do that and proceeded to threaten with two choices:
1. Call the police and have them resolve the matter.
2. Sign a paper admitting to the trespass and they will bill me a fine of between $100 to $200 (the product was $8).
I wouldn’t sign the admittance paper and after they called their boss, they just had me sign a trespass notice according to which I may never set foot in the store again. However, they said that they still will send me a fine notice attached with a phone number and said that if I don’t pay the fine, I’d have to call the phone number to setup a court date.
When I left, I said “see you guys in court.”
Few things to state:
1. I did not know that breaking the wrap/foil/seal is classified as theft (no notice of it anywhere).
2. I did not have intent to derive the owner of the product.
3. If they notified me immediately that I would have to pay for the product, I would pay for it, the fact that they waited until I exited the store before cornering feels very much like entrapment.
I need help with this one guys, I feel like I am right. Maybe I shouldn’t have broken the wrap but I don’t think it’s theft. I am ready to fight this in court (admit but deny intent doesn’t classify it as theft, correct me if I am wrong)
Thanks
BTW: Washington Seattle area