
Could be right with the baby hamster theory.
If the number they rang is a freefone number there is a good chance it is someone mucking about.
We used to get comedians ringing the funeral service - one evening they sang "ooh ooh ooh ooh, staying alive, staying alive" emergency lift phones were favourite, usually with kids. Another freefone favourite with kids was Save the Children "save me save me" you had to assume every time that the call was real until you were sure it wasn't.