This bug does not have a 100% repro but I got it several times already.
Sometimes, as an elf, when you try to eat a corpse from your inventory, the "memory dialog" will not play correctly. If the corpse was supposed to give you a skill, you won't get the skill neither.
When I encounter that bug, I always eat a piece of flesh from my inventory by left double-clicking on it.
To avoid it, you can reload your last save and hope the bug does not appear again. If it does, reload as many times as needed.
