In Wisconsin, regardless of which party the agent represents, they are required to keep confidentiality of all parties. If you specifically told the agent not to convey that you had interest in the property then the agent is bound by those instructions . Whether your strategy to avoid competitive offers would have worked or not, (you would be surprised how fast we can get those competing bids in - LOL) it was your right to have those wishes respected. I hope everything worked out and you were able to get the property you wanted.
Just another comment on multiple offers. I noted a comment from an agent in Georgia about the rules in her state requiring highest and best. That is not a law in Wisconsin (or even a usual way of doing offers in my area) . The Seller can accept, reject, or counter any offer in any manner they choose, no matter the order it was received or the quality of the offer. They can respond to one, some or all of the offers received at their choice. A Seller does not need to respond to, or act on, any offer for any reason as long as they are not discriminating. Asking for highest and best might be a valid option to get all buyers to come up to their top dollar. However, I do not want a buyer to think they will get a second chance if their offer isn't the best because a lot of times that will not be what happen !!!