Thank you Alhaxit for your suggestion. I have done what you suggested and hope it solves the problem.
It troubles me that someone has the capability of identifying outgoing searches, using the search title and then posting an obscene message.
Do you know if it's possible to identify the person responsible? I know very little about the internet and how computers are linked together, but there must be someway to stop this person from ever sending obscene content in the first place.