It should not be possible to brick the Clip+ by simply using it, the unbrick procedure should only be necessary when flashing a new OF fails, or if a bad bootloader was flashed.
Did it refuse to come back to life after plugging it on USB to charge it? (after making sure it's powered off or discharged; 2 weeks should be plenty enough)
If the reported drive is 4MB then you should attempt the unbrick procedure again until you see the correct size, it's very difficult to have the correct drive come at the first attempt, for me it always required between 3 and 10 attempts until it worked.
SansaAMSUnbrick says
If it doesn't works, try to repeat it several times.
but perhaps it's not explicit enough.
If you have a soldering iron available you should try to unsolder the battery (only the + or ground wire should be enough) so you are sure that the device is off before plugging it on USB, and you are sure that it isn't causing problems.
If the battery is disconnected the device will run off USB power and you are still able to perform an upgrade.
Note: you should be using the same OF file that you had on the device previously to perform the upgrade (ideally patched with the same rockbox bootloader that you had)
Finally if you give up and decide to get a new one, don't throw it away; the parts can still be useful (and if you don't want to keep the parts then i'm sure a rockboxer could have a use for it)