In episode 16 Suzuha goes back in time. Unlike what happens when they send a D-Mail or time-leap, this doesn't cause the divergence ratio to shift — which in turn means all lab members still remember her, since she was just there.
However, after that, Mr. Braun goes to the lab to give Okabe Rintarou a letter from Suzuha, saying:
It's a letter from someone who once took care of me.
Does he not remember her working for him as a part-timer? That would be weird, given everyone else in the lab appears to still remember her.
Or is the name change — from Amane Suzuha to Hashida Suzu — along with the age difference enough to make him not realize they're the same person?