No. Although Article 16 of the NAR Code of Ethics prohibits REALTORS® from engaging in any practice or taking any action inconsistent with exclusive representation or exclusive brokerage relationship agreements that REALTORS® have with clients, Standard of Practice 16-3 allows REALTORS® to contact the client of another broker to provide a service different than what is currently being provided, or to offer the same type of service for property not subject to a broker’s current exclusive agreements. If you are offering property-management services, another broker can provide brokerage services to sell the same property without risking violating Article 16. And if your owner had two properties and you only managed one, another broker could provide property-management services for the home you don’t have an exclusive agreement for.
However, information received through an MLS or any other offer of cooperation may not be used to target clients of other REALTORS®. In your situation, the other REALTOR® did not use these methods, and is therefore not in violation of the Code.