I need matches to light the lantern but they are not on the fireplace mantle. Is this a bug? Do I have to do something to make them appear?

You have to break into Von Zell's room first. You do that by going into Preiss's room, getting the rope, going to the window, and using the rope on the window. There are 2 things you will need to find in VZ's room before you leave.

Also you should talk to Von Aigner and Henneman and show Hilda and Parsival's Tags to Dr. Klingman. After you've done all these things the fire should be lit and there should be a box of matches on the mantle.