Ouch. Suppose you have a fiancee. You've known her for 7 years. You're one month from getting married. Normally you call her every night after work saying you're done working and coming home. Suppose you forgot your mobile phone tonight and find yourself unable to call her. Suppose coming home and walking in on her having sex with the plumber.
That's what happened to my colleague's brother. Needless to say the wedding's off.