Yes, and again no dice.have you tried just sda without a number?
I have tried multiple USB flashdrives, all of which have a similar behavior. I have attempted to boot with the device inserted, and as soon as the device successfully boots, the light on it turns off.Is it a usb 3 flash drive? Theoretically it's supposed to be backwards compatible with usb 2, but if the port on the router is a cheapo one, there might be some issues.
I can't think of anything else, really. Have you tried booting it with the drive inserted and then mounting?
Just as an FYI, I am using the device with a built in battery.