"Oh Bagman's likable enough, of course, but how he ever got to be Head of Department ... when I compare him to Mr. Crouch! I can't see Mr. Crouch losing a member of our department and not trying to find out what's happened to them. You realize Bertha Jorkins has been missing for over a month now? Went on holiday to Albania and never came back?"
-- Percy Weasley, August 1994 (GF5)
She is missing for over a month at the time of the Quidditch World Cup of August 1994. Her Head of Department, Ludo Bagman, is too busy — and irresponsible — to send someone to look for her. Voldemort uses her murder to create a Horcux out of Nagini (BLC).