He wanted to believe Percy was right, that there was something he could do, only he was too intelligent to really believe it. He knew there were no options left, that he either did what Rodolphus wanted or didn't, and if - when - he didn't his mother would be tortured until she couldn't take any more and then disposed off.
Miles hadn't even been able to find out where she was held - if he'd at all tried. Why would the Aurors do any better? Even if they did, what were the odds of any of them being able to go where ever this place was?
He didn't know how to tell Percy any of that though, knew that Percy knew it too but would keep repeating that there was hope where there was none.
'I won't do anything stupid again,' he assured him instead, his voice strained as he leaned into to Percy, craving the touch as if it was air. 'I just wish I wasn't so helpless, or useless, I should have reacted the day she didn't write back, I should have moved her that very day, taken her somewhere safe.' He'd been over what he should have done a million times in his mind, yet he knew there was nothing to keep him from the truth - he should have, but he didn't. He'd failed, and because of that his mother was now... he didn't even want to think of it.