One possibility might be to use an EEM script. You could configure the script to use tracking to some address reached through the EzyVPN. If you lose connectivity the script could show log and write the output to a file in flash.
Thinking slightly outside the box it might work for you to have a PC connected to the console port of the router, or connect the router to a terminal server and have a PC connect through the terminal server (so that the PC does not need to be physically near the router). Have the PC let the terminal emulator run displaying console output. They can reboot the router but the log messages are still in the screen buffer of the PC.
HTH
Rick
HTH
Rick