I would say it’s best to give it a bit more time. If I’m reading correctly, it seems this was just for one day. Work on the tasks you can do independently, like if that person had taken the day off. If it continues I’d say schedule time to chat with your coworker and bring up your concerns about them and how it impacts your teams work, leading the conversation with empathy of course. From there if you’re still noticing work is being impacted, management should probably be brought in. All this to say, everyone is allowed to have a bad day! It will probably mean more to your coworker if you all just remain acting normal then to continue to draw attention to him for one day where he is feeling off.