Alrightokayfine. It's not a drabble, it's an explanation, but it's all I have the brain space for right now.
Remus saw the Trio disappear in the entrance to the Whomping Willow and decided to follow them, dodging stray curses and hexes as they headed for unknown targets. He stayed behind after the Trio left, hidden in the shadows of the passageway, and slowly made his way up to the Shack to see what had transpired. Upon seeing Severus, he immediately rushed to his side and did his best to staunch the flow of blood. He grabbed a chocolate bar from his pocket – it's a magical elixir as far as Remus is concerned, and so he always carries one – and offers bite sized pieces to Severus. Remus knows it won't do anything for the poison in Severus' system, but the chocolate restores magical power. Remus correctly assumes that Severus – a preeminent Potions Master – will be carrying anti-venom and blood replenishing potions on his person, and so once Severus has regained enough strength from consuming the chocolate, he directs Remus to the hidden pocket of his robe, muttering something about 'being expeditious' and 'not spilling a drop, you infernal wolf'. The combination of these factors allows Severus to stand with Remus' help, and together they make their way into the castle from another passageway and seek out Madam Pomfrey.