We saw Severus leave the ward in the last chapter. I didn't point out how he left or what direction he took because it would've been too tedious. He could've left through another exit that allowed him to avoid being seen by Harry's group. Or he might have slipped through Harry's notice because of his anxiety. Either way it wasn't important enough for me to describe.

About the commas *sighs* everyone has their own opinions of them. Some think they're too much, others too little. *shrugs* It works for me and that's who I always strive to write for. :)

Thank you for reading.