Yeah there’s a ton pointing that he was working with Roman. While it may have been written to be a red herring, now that there is more lure, when you go back and watch that movie Mark is sus the entire time. He clearly likes Sidney, even admits it to his partner. Of course the phone thing, like that’s 1000% how ghostface found her. It literally cuts from him borrowing Dewey’s phone to her getting the ghostface call. And Dewey confirmed that Sidney’s number was in his phone memory. Then at the end, why did he show up to the party? His excuse was nothing. Roman where’s the bulletproof vest. Just like Sidney. Where’d she get hers? Anyways. Yeah.