Well i think this is first time because he mentions that when he met her he had no clue why he couldn't read her which suggest that if he had met one before he would know the reason. Let not forget when we started 4 years ago he hardly ever used his power it's was only when he became involved with cops he started explore his mind reading abilities.
I don't particularly like the direction this series had taken because in first season direction was he was trying find his mother but they have completely forgotten about this storyline changed to a police drama.
. They even forgotten his flashback he was experience and lastly what happen all those migraines he had in second season from using his powers ?