Hawkeye and Trapper know that Frank would fall for their scheme of finding gold in the hills near the 4077 and he fell for it in a big way. Frank had even convinced Margaret that the gold was real. It was always fun to put something over on Frank, but when it increased their workload, they realized it wasn't such a great idea. Yes, Hawkeye and Trapper's mission had been a success. Frank was staying and their workload returned to normal. But now that the ruse was over, one thing was for certain. They sure would miss driving that gold jeep.