Marco had blown off the second half of the school day. Some things were more important than sitting in class. It was unusual for him to skip, but he'd make an exception for Nico.
He made a point to tell Star he was leaving, so she wouldn't worry. Less than half an hour after Nico's first text, Marco was making his way up the path to the cave.
"Nico? It's me," he called out, so Nico would know he was coming over the ridge and into view.