That's the first thought that springs to mind, but not necessarily the case.

Aircraft from that era were quite solid and they did not have a pressurized hull. The Lockheed Electra and other similar aircraft from the same era flew in wartime operations and regularly came back full of holes.

A single window broken cover should not bring an otherwise sound 1930s era aircraft down.

Exactly correct. There is no way a missing window would bring down the plane, especially the back window, unless by some freak accident the patch damaged a control surface on the tail by breaking free. One can think of an almost limitless list of more likely hypotheses.

To be completely fair, a list such as insulating foam peeling off and striking the wing (http://en.wikipedia.org/wiki/Space_Shuttle_Columbia#Final_mi...) or a random bird striking a plane and causing a failure (http://en.wikipedia.org/wiki/Bird_strike#Incidents)? I'm not saying it happened, or even that it's likely, I'm saying stranger things have happened.

Regarding this being the only piece found... if they needed to get parts off the plane for use as tools, this patch would be a good target piece of metal to go for prying free. I still feel the odds are pretty slim but they make an interesting (if sketchy) case. Hopefully something more concrete will come up in future.

Planes could take a lot of beating and still fly. Grandfather flew a bomber in World War 2 and planes would come back with hundreds of holes. Losing a patch should not have brought down the plane. A modern airline, yes, it could have a much bigger effect. Pressurized hulls, electronic flight systems etc are more fragile.

reminds of a HN favorite story, about how the study of bombers links up with work done today

http://www.fastcodesign.com/1671172/how-a-story-from-world-w...