Every single boss in the area is dead the moment I enter an area bug. Did someone hacked my game?

So every single boss is dead. As I was walking through the mountain tops of the gaints I randomly got an ancient dragon smithing stone which is only dropped by the night's cavalry in the consecrated snowfield. Then I got five dragon hearts, death ritual spear, explosive ghost flame and a bunch more items. These are items dropped by the open world bosses. I went to Castle Sol and guess what, Commander Nial is dead too. Pretty much all the bosses are dead and the fire giant is also dead.

Possible cause: Is it a bug or did some script kid hacked my game

The 'bug' only happened after I fogwalled an invader player in the Gaint's Mountaintop Catacomb. The funny thing is it's kinda his fault. The whole gimmick of the dungeon is the lever is under an elevator and the invader was losing the fight so he ran to the elevator and escaped up which means he kinda help me through the dungeon because the way forward was under the elevator he triggered. I wasn't going to wait around so I just continued and went to the boss door. The invader knowing he was not gonna catch up waited for a while then returned home and guess what this was when the 'bug' happened.