Is it bad that while watching that early scene in Dark Water with the lava I was over here saying “Well, good thing Jack still has a key and there’s a phone on the outside of the Tardis.”
Could you imagine the awkwardness of that phone call though? “Uh, hi Jack, it’s been a while…manipulator still working? Good. I need a favor…”
That whole scene I kept wanting to shout at the screen, “he can just snap his fingers and open the door. there’s no fucking threat here. it’s not like he can’t get in without a key, seriously. you don’t put a key in to fly the TARDIS. wtf is the point of this scene.”
The other thought was, yeah, “Jack’s got a key. Couple of other companions too (don’t believe Martha turned hers in either).”
Jack, Martha, maybe Mickey. Oh here’s a sad thought. I bet he left one with Donna and it’s just that odd key on her keychain that doesn’t seem to fit anything but she keeps it anyway and doesn’t know why.