^If I had carried a 1911 to hell and back, had it save my life more times than I could count. I wouldn't want to give it back to the government. I am sure this is a mindset a lot of those soldiers took. Stamped government property or not, the gun should survive with the solider as long as the solider is alive. Many of them probably took this view, and did whatever they could to keep it...
Like you said keeping it was probably about as simple as cramming it in the bottom of a duffel bag and brought home.