athass_prkr
It is obviously a trap. I'm sure Tom did it to see who would run for the entrance...and now he knows it's Harry. Your MC could have at least ducked under his cloak before checking…so he wouldn't get caught if anything happened. I just hope it won't be the classic "Harry is the heir!" because it's starting to get too redundant in fanfics. Your character should at least remember that it's better not to run towards the attacks... that he at least makes sure with the map that no one is around to accuse him.
I still don't believe its Lockhart,he's a coward and a conman,not an idiot.I made a essay on why he didn't have the diary and I still think most of those points still stands.Not only that but I don't think Lockhart was on the train,or at the part on the train,when Harry saw the diary again.It most likely Riddle trying to trick whoever trying to find him.That or its one of those junior professors that keep being talk about here and there.Its unlikely,but it could be a house elf,we never got the race,only the age and sex,so its possible.And it can also explan why the person just keep disappearing.