1) Physically trace the power cables.
2) make sure everything is showing green. It will also say that the cluster is back to normal
3) yes, but depends on what got unplugged fully. If the controller got unplugged, it would be treated like a power failure. If I shelf dropped.... You'd have a really pissed off Filer with some not happy aggrs. (Had that happen onces, but everything came up cleanly after it was sorted out.)