they were stupid kids who you later see are just kids and are scared and not "hard" in any way. He wouldn't have used it.
Nope, not convinced. He was more than happy to go after that "dog" that attacked him, so it is not a huge leap of the imagination that had she fought back that he'da used the knife to "fend her off". Do you REALLY think, if she'd said no and walked away, that they'd been all like "ok then, sorry for bothering you, have a nice day lady" ?!
Oh yes, and "being a scared kid" doesn't make you reluctant to return a treasured ring to its owner just cos "it's your ring now and is all shiney 'n stuff". :nononoononono: