Nope. He was not texting anyone at the "exact same time that he erased Cooper from conscious memory" and that isn't a small detail.
He didn't text anyone at all from seconds after 9:15 until 9:24. Cooper was in his sight from 9:18 as they walked out of CFA until RH strapped him in, how ever long that took.
Whatever alleged "erasing from memory" or brain scrambling that took place came between the time Cooper was strapped in until the the time RH went around the Uturn and didn't immediately get in the left turn lane.
RH had already "forgotten" Cooper by the time he reached the intersection, around 9:24.