Restoring back to pure stock for warranty replacement

My phone is screwing the pooch, and I opened a warranty claim. I reflashed back to stock from the U firmware following the instructions at http://ift.tt/2asjEmT but that custom lock is still on the boot screen. Is there a way to remove it? I googled around and found Triangle Away, but I am not sure. Any ideas?

from xda-developers http://ift.tt/2a4ZFHz
via IFTTT