To put it shortly, Bokuto was worried.
Bokuto had to go to school early to make up for a test that he may or may not have failed, so he hadn’t been able to walk to school with you and Akaashi. And then on top of that, you weren’t at lunch, and when he had texted you, you simply sent him a dry response that read “finishing an assignment.” Followed by “I won’t be at lunch, sorry.”
And Bokuto may not be the best at picking up social cues, but he knew you were never that dry! You always texted like he did to match his energy—which he really liked!
And then once practice started after school, you still weren’t there! When he asked Akaashi, he simply told Bokuto that you had been acting off all day. So he was super worried about you, because you always let him or Akaashi know if you won’t be at practice, or anything, really.
Thats how Bokuto ended up at your front door, knocking.