Then it's probably a different group than Snake's, sadly. Unless they're being stupider than normal, which one would think they'd get smarter since Gosho's skills have increased a lot since their first appearance. Because Kid was the one they killed, even if they're still convinced they missed, not Phantom Lady...
DUDE. Maybe AOKO'S mom is Phantom Lady, and we've got it all wrong! Hear me out!
The hairclip is obviously going to be important, because you're right, that is out of character and conservation of detail decrees it important. The hairclip looks like the Eiffel Tower, which is where Toichi and Phantom Lady first met, and where Toichi first appeared. MAYBE the hair clip is important because it's a memento of Phantom Lady's that she got in Paris when she met Toichi. Aoko found it in her house, thought it was pretty, and put it in her hair. It would explain why the group thinks that Nakamori is Kid and Aoko is Phantom Lady perfectly. Say Aoko's mom dies when Aoko's a baby, and Phantom Lady conveniently disappears. Years later, Toichi dies on stage and Kid disappears. BUT Nakamori was a friend of Toichi's, so maybe the group is reasoning that Kid!Nakamori got scared because his friend was killed and Nakamori thought it was a warning. And then when Aoko is All Grown Up she can play Phantom Lady, and so the group reasons that Kid!Nakamori comes out of retirement to teach her the ropes. (Still doesn't explain all the head of Taskforce alibis, but they're idiots, obviously.) Kaito's mom, meanwhile, is suspicious for the sole reason of being in on the secrets of both Toichi and Aoko's mom. She knows (because she was buddies with Aoko's mom maybe) about the fake Ryoma stuff and, without telling Kaito about Aoko's mom, gets Kaito to do that heist. So Kaito meanwhile still has no idea about the true identity of Phantom Lady, and thinks it may be his own mother, hence his words at the end of Patriot Kid.