Sirius got held up at the pub. He had requested the day off, and had only gone by to pick up his pay but Joe had called out sick so Sirius stayed on for as long as he was able but he really really needed to get back to his flat before the portkey was activated.
Since Joe had called out crying food poisoning or stomach bug or something, Sirius made a grand show of groaning and cramps and mad dashes to the bathroom and it was enough that Mitch, the owner, told him to go home. No one wanted their drinks from a retching barkeep.
He hurried home and opened the door, certain that Jim was already there. He'd be late, as was often usual. "I'm here," he announced grandly, ducking down to press a quick kiss over Remus's mouth.