The traditional concern of runtime verification is the ability to detect an incorrect system behavior and maybe to act on such systems whenever incorrect behavior of a software system is detected [20]. In this paper, our concern is to provide a system observation through which the system behavior could for instance be diagnosed, e.g., to resolve unexpected bugs. Such a system observation is elaborated from a partial observation. Our work is at the protocol level: given a distributed application relying on a FIFO protocol for message passing, our concern is to reconstruct a full execution given by its observable send events.