This paper proposes an ad-hoc routing protocol using unicast-based route discovery in a hybrid wireless network, ECCA, which combines ad-hoc networking scheme with a centralized hierarchical network. The network aims to collect damage assessment information in disaster circumstances, maintaining connections between a base station (BS) and nodes by way of multihopping. In the event that a direct link between BS and a node disconnects, the node switches the mode from a cellular to an ad-hoc mode in order to access BS via neighboring nodes. A routing protocol proposed in this paper builds a route by way of monitoring neighbors' communications instead of broadcasting a route request packet. Experiments show that approximately 90% of nodes can discover a route within a few hops, even if only 20% of nodes are able to access BS directly. Even in a low node density, the network is capable of transferring data within three hops.