Donnie does look at Sonic then, but he's hardly psychic so he has no idea what's supposed to not be mentioned. He frowns a bit, looking dubiously at the hedgehog once the other is getting to his feet. "I'm pretty sure you didn't tell me everything," he starts, because he's totally helping here.

But now Robotnik's following up in his interrogation and the turtle frowns as he looks back at him.

"Yes, it bothers me- but not in the matter of sentiment! There's so much that can be repurposed! Broken tools might not have much ability to be repurposed but parts can be, and if nothing else, well, there's still the metal! Look, I don't know where you get your material from but I've had to salvage and scavenge everything for anything I've ever built."