This is not a derogatory term and while these problems are annoying and time-consuming the lack of explanation does not automatically place blame on the user.
The term is based on the classic Warner Brothers short, "One Froggy Evening", in which a singing and dancing frog will only perform for the construction worker who found it.
IT Helpdesk: "OK, I'll come down and have a look."
IT Boss: "Did you fix User's problem?"
IT Helpdesk: "I couldn't find any problem, no matter how hard I tried. Guess it was a singing frog."