Pedro

Cleric Pedro was a cleric soldier who helped to investigate the crash at the Byzantium. (DW: The Time of Angels). Later, he was left to help protect Amy Pond along with three other clerics. He was sent to investigate the mysterious light along with another cleric, but was absorbed the Time Field crack and forgotten along with his companions. (DW: Flesh and Stone)

Before Rory Williams was erased by a time field, Amy remarked that she could still remember the clerics, even though they could not remember each other because they were not time travellers like her. (DW: Cold Blood)

Since the Cracks were sealed off, it's likely Perdo was never erased from existence.