It wasn't He Niancheng but Gu Qian.
Gu Qian probably texted her because she didn't see Gu Qingjiu when she woke up in the morning.
Gu Qingjiu replied to her, 'Applied for leave because something cropped up.'
Since Gu Qian should be training at this time, she wouldn't get to see her reply.
Seeing that He Niancheng didn't send her any other messages apart from the one last night, Gu Qingjiu felt an emptiness in her heart.
As she walked out of the alleyway, she gave He Niancheng a call. Shortly after it started ringing, someone picked it up.
Without waiting for Gu Qingjiu to speak, He Niancheng spoke first. "Where did you go last night?" He sounded calm and not particularly anxious.
Gu Qingjiu, who had been feeling sheepish before this, stopped feeling so.
"Something cropped up," she said, sounding justified.
Why wasn't this person at all anxious after she disappeared for a night?