Hi Nancy, Quizzes are always in the state of being put online and being taken offline. Occasionally, quizzes are deleted from the database. When that happens, anyone who played the game may notice that their score goes down that number of points. It's just kind of a part of the whole process - something everyone has to endure.
Quizzes are not deleted on the spur of the moment. One of the main reasons they are removed is when a quizmaker's account is terminated. (Deleting accounts is something that happens when a person repeatedly violates Quizzyland policies or when a person deliberately does something that is against the stated rules of the site. They are always given a warning before the account goes. When the account goes, all of that person's quizzes go as well.)
I know it's really frustrating to see your score fluctuate like that! But, realize that it's not just your score that's doing it. Everyone else affected by the quiz in question experienced it, too.