From: Near Portland, OR
It's very difficult to prove that something did NOT happen. The only way to 'prove' she didn't make it to Gardner Island is to find her plane 17,000 feet down 100 miles away. And since that is unlikely, we will likely never know what happened.
Her plane is a lot smaller than Flight MH370 and the search area larger (although the weather is better).
Additionally the search for Ehrhart's plane is made all the more difficult by being a smaller plane, more fragile, lost close to 80 years ago, and they didn't have any of the tracking tools we have today that gave us some leads on where MH370 went.
We'll know more when they investigate the anomaly found on the sonar sweep, but I suspect it will turn out to be a false lead. It could even be part of a WW II aircraft down there. That part of the Pacific wasn't the most active region during the war, but the US was running ASW flights out of every spit of land by the end of the war. I believe a Ventura is a little bigger than an Electra, but they are in the same size range.
WitP AE - Test team lead, programmer