This happened to us too. Playing coop with 2 friends. While I was literally spending ages scouring the town for those damn scoundrel books, my friends finally lost patience and said "Ok we will continue while you look". They proceeded to murder papa.
15 minutes later I googled who had the skill books and I'm on discord like "Guys, you know that dwarf you just killed? The ONE npc you decided to murder?" They go "yeah?" and I'm like "HE HAD MY FUCKING SKILL BOOKS!" and they were crying from laughter on discord.