Draco had not been expecting visitors. Hearing someone come in, he looked around quickly for a hiding place. The workshop had a lot of cabinets and so on, but they were all full of potions ingredients and probably not big enough for him to fit in anyway, even with his current sickly-thin state. Damn. He'd been getting close, too. He wasn't sure whether what he was making would be completely safe.... but hey, that's what experimentation was for right? And no one had specifically forbidden him from doing it, right? That kind of logic had always served him well back in school. Well, most of the time.
He decided to stand behind the door and hope that whoever came in just wanted to nick some Amortentia or something, and wouldn't come all the way back to the workshop. Also that there was no smoke coming under the door or that the smell of the simmering potion was strong enough to alert anyone that he was there.