I think this error is not releated to power supply failure. This is Bug CSCef80423.
Switches can unexpectedly reload due to an unknown cause.
Upgrade the switch to the latest Cisco IOS Software release unaffected by the bug in order to resolve this issue.
The same error will get when you entered show version command in Cisco Catalyst 6000/6500 series switch.
System returned to ROM by unknown reload cause - suspect
boot_data[BOOT_COUNT] 0x0, BOOT_COUNT 0, BOOTDATA 19 (SP by power-on)