Mystery Man discussion

hi! i'm trying to found this book I read last year, I only remember a few details about it so this is a big stretch, but hopefully someone has read this book and knows what I'm talking about!

So what I remember is that there is this person (I think a teenage girl) and she is trying to solve something, i think to do with missing people but I'm not really 100 percent sure. So she gets a text from someone to meet her somewhere (details i am unsure of) i think this somewhere was something underground? anyway, the person she meets injures her ( i think she got stabbed) and she gets her hoodie all bloody. she goes to her friends house whose mom is a doctor and the mom helps her with her arm.
also it was young adult!!!

somehow this is literally the only scene i remember, but hopefully it is familiar to someone!!
tysm!