A concurrent system specified as a rewrite theory can be symbolically analyzed using narrowing-based reachability analysis. Narrowing-based approaches have been applied to formally analyze cryptographic protocols and parameterized protocols. However, existing narrowing-based techniques, based on a breadth-first-search strategy, cannot deal with generic distributed systems with objects and messages due to the symbolic state-space explosion problem. This paper proposes a heuristic search approach for narrowing-based reachability analysis to guide the search for counterexamples involving a small number of objects. As a result, our method can effectively find a counterexample if an error state is reachable. We demonstrate the effectiveness of our technique using a nontrivial distributed consensus algorithm.