Translation:We thought about you yesterday during the concert.
@Jojo53168 Why does imparfait sound weird? Is it because we're talking about a mental activity or stare?
Or is it because penser à is always a quick one-time occurrence? It takes only a second to "think of somebody", and passé composé would be the best translation. But to "think about somebody" could take much longer, and require the imparfait. Like maybe nous réflichissions?