All depends. If I just drove five hours (or more) and took a week off of work I'm not stopping the hunt early on the first day because of an unfortunate lost bird.
By the same token I've packed up a hunt and pointed the truck towards home early on the last day of a long hunt after losing a lightly hit rooster. In that situation we had our share of memories, our share of roosters in the cooler and the dogs were tired and well satisfied.
Maybe I can be accused of being morally flexible but I don't think this issue has to be thought of in absolutes. One of the serious realities of this sport is that game will be wounded and lost. How we each come to terms with that is varied and personal.
The real obligation is to make an honest and determined effort to find the lost game in the first place.