This paper presents a method to map user needs and integrate serendipitous search behaviors in search algorithm development: the living lab approach. This user-centered design approach involves technology users during technology development to catch unexpected insights and successfully innovate. This paper focuses on the preliminary findings of a living lab case study to answer the question how this methodology reveals fine-grained information about users' serendipitous search behaviors. The case study involves a specific user group, media professionals who work in broadcast television and use audiovisual archives to create audiovisual content, during the development of new search algorithms for a large audiovisual archive. Research insights are based on data gathered during one co-design workshop, and ten in-depth semi-structured interviews with media professionals.