The test Madam Pomfrey conducted on him allowed her to test against other people's magical signatures and see if there was a match to make. It was a very uncomfortable thing, but Hermione's presence was a godsend.
"She'll find out who did this, Harry. Right, Madam Pomfrey?"
There was a moment of silence, and then she was nodded. "We have all the means to find out who did this. Now it's just a matter of time…"
There was something about the way she said that that got Harry worried. He sat up against the headboard, pulling his legs close to him. He was wondering if he should just say now about the Slytherin Prefect badge, but doing that was probably more embarrassing than the test he'd just taken was. He couldn't do it. He'd rather live without.
"Can you really find the person?" He asked her.
"If it was Polyjuice," she said at last, not quite meeting his eyes, "depending on how good the brew was – the magical signature might not…" she looked at their worried expressions and breathed a deep sigh. "I hope we can."
Harry wiped at his face, very stressed. "I can't believe this happened…"
Hermione held his hand in both of hers.
Pomfrey came over with a Dreamless Sleep potion. "Take this, Mr. Potter. Get some rest. We'll have more information in the morning."
Hermione helped it to his lips and she caressed his head as he laid down, the blankets tight around him and up to his shoulders. "I'll stay here, Harry. Don't worry."
Harry felt the drowsiness envelope him, and in a state of weakness, he began to shake with sobs. Hermione cooed him to sleep, whispering that everything was going to be okay. Harry's last thought was that he didn't want to stay at Hogwarts – not for a little while, at least. He wanted to go home – that in and of itself was a mindboggling thought to have considering what sort of home he'd be going to.