Arriving almost at the end of the campaign, I realized that I had not found all the artifacts, so I decided to look for a guide that would show where all the items were. Seeing item by item, two are missing in my bagpack: Power Brick and Defribrillator. In a video on YouTube, I picked up the locations and went to get the artifacts, but they are not there, nor in my backpack. In the video some people comment that they are having the same problem with different items. Does anyone know how to solve it? Is it a bug?
You’re sure that you didn’t find the power brick in the back left car of the ferry on Sea of Titans and the Defib on the right room, second floor of the House of Bones? If you can’t find them there then it may indeed be an issue but over my multiple runs of the game I’ve never had an issue with Artifacts not spawning in.
Hey, thanks for answer.
I’m 100% sure about it, later I’ll share an screenshot of the back left car of the ferry on Sea of Titans, and another showing my items on bagpack.
By the way, here’s the video guide reference (YouTube). See the comments section: cMJ-XdFWaCQ.
Then you may indeed have a bugged save, sucks to say it but short of editing your save file some how to add them in you may be doomed on that file.
Had the same problem, no Defib at the 2nd floor first room. But after I killed all enemies in this area I came back to check and there it was - in the last room, ground floor… 
It sounds like an explosion might have gone off that caused the artifact to drop and bug out, did you kill the pyro near it?
Some users are commenting this, but in the Sea of Titans, for example, there is nothing to be broken on the spot. There are not even enemies, I killed everyone in the most stealth possible way. I will not go back the whole game to get the artifacts…