Does failed RPC affects anything?

I have a problem with my zombie game. This is the thing that happens: when the client shot the zombie, it sends a RPC to te server to hurt the zombie, and when the zombie dies, the server sends an RPC to everybody telling that the zombie are dead. The problem that happens is that, sometimes, after i killed a zombie, before i receive the deadzombie RPCcall, i can shot the zombie again and send another hurtthezombie RPC to the server. When the RPC reachs the server, the zombies is already dead and i got the error "NetworkViewID did'nt found during lookup, strange behaviour may occur" (something like that). Does that makes any diference? Do i need to fix that? And how?