A wannabie asked some good questions regarding cleared vs filed flight levels a few pages back.
If your filed flight plan called for a level change, would you do so without clearance if you had lost contact with ATC?
I wouldn't. Not if I thought the loss of contact was due to poor coverage.
I would change altitude without a clearance if I was sure I had suffered a comm failure, but that is a different issue than a loss of contact. In most cases, anyway.
As for switching the transponder off/on, what if they did have an intermittent transponder? Poor connection? The mid air could have fixed that. Just a different version of "a technical knock".
Regarding offsets, I'm sure it's buried somewhere in the Jepps text (ATC) manual, that we are allowed to offset 2 NM to the right in areas with limited radio/radar coverage.
Maybe somebody can confirm or deny this?