The whole thing was horrifying and heartbreaking. Having to sit and watch Sirius go through so much pain nearly destroyed what was left of Remus' heart. How could someone inflict such cruelty upon another person and induce such suffering? He knew what Severus was doing would get to the root of the problem, but he feared for Sirius whenever it came to the surface. There were tears prickling his eyes, but he managed to swallow them back, just as he'd been doing for days, weeks. This had to be about Sirius, not him. He promised Sirius he would be there for him, to see this through and never give up. Gryffindor courage was all he had left to rely on.
His eyes were still on Sirius' limp body when Severus indicated he'd finished what he came to do. It brought him out of his thoughts, but he had hundreds of questions. A statue was triggering those outbursts? How was he supposed to get Sirius around it without passing it? What was it? Was it enchanted? Could they break whatever curse was put upon it? Or destroy the statue? What was going to happen to Sirius now? So many questions, and no answers. Before he could even speak, Severus was making a snide comment about his relationship with Sirius; apparently he'd seen that too. That was of little consequence to him at the moment.
There was temptation for him to follow Severus, but he was already taking to the stairs. Remus followed him to the door of the dorm room, but stopped there. He couldn't leave Sirius. He had to be with him when he woke up. ...And it would probably be best if Severus was gone. If James came back, all hell would break loose. It was going to be bad enough anyway whenever he told him about what he did.
Sirius. He had to focus on Sirius. Communication with Severus could continue over journals.
For now, he went back to Sirius' bed and started to undo the bindings keeping him tied down. He didn't want him to be restrained when he woke up.