Simply put. If you fire and hit something, that something is going to take damage. There is only two ways that cannot happen. If either end hard disconnects from the server, the packets cannot be delivered.
A hard disconnect is defined as the computer blows up, or the ISPs routers all die at once, or the server blows up, or something similar.
Is it possible for a packet to time out or exceed retry limits? Sure, but the numbers for that are so extravagant as to not really be a factor.