Turns out he wasn't.
He was in the 1850 and 1860 United States Census listed under the last name of his step-father--whom his mother had married in 1849. Until I discovered the last name of the step-father, I was unable to find Ira.
Is it possible that your UFO ancestor wasn't dropped off by aliens but was instead listed in records as a child under his (or her) stepfather's last name? And that the first time they used their "birth name" in a record was when they married?