Before you race out to make claims of unethical behavior, it would help to first confirm that such a situation actually existed. This is one of the reasons that I insist that every offer presented and rejected by the seller be acknowledged in writing to ensure that the buyer knows that their offer was received and reviewed, but not accepted. If you can confirm that the offer was not presented to the seller and the seller never saw it, then THE SELLER (and not you) would have a claim, if the seller wishes to press that claim with the proper authorities.
Truthfully, the listing agent is NOT your agent, and has no relationship with you or your agent. The listing agent, however, does have the fiduciary duty to the seller, so if there are any damages--and if the offer that was accepted was a lot lower, there could be damages--then the seller, and only the seller, can assert those claims. You, as the buyer, actually have no damages. Yes, I know, you did not get the home, but again, you are not out any money and have not been damaged by not getting the property, so you have no claim--you were simply not enriched (by a home) in the manner you wanted, and that's not a claim, but simply disappointment.
You can certainly talk with the seller since you are not in contract with him/her and let them know what you made an offer. After that, however, the decision to make a complaint lies with the seller, and not with you.
Sorry to be so candid, but I do not want you to agonize over or expend lots of energy for an issue that will not resolve your problems, not change the situation, and will not result in punishment of the Realtor in question. Okay?
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