I'm sorry, but this is total codswallop.
http://snopes.com/rumors/warning.htmYour message has been told a million times exactly like this. It's false.
Let this be a lesson not to believe the silly stories on the internet please. Or, in this instance, your 'friends Mum'.
Contrary to wishes, i'm going to close this topic to head off the coming panic it will probably cause for nothing. If you wish to do something about it, talk to the local police, although you'll probably get the same reation.