I heard somewhere Agatha Christie disappeared for some time and returned but no one knew where she had been---Is this a fact or was it made up to replicate one of her mystery stories ?
It is true,she disappeared for 10 days in 1926.The film Agatha starring Vanessa Redgrave is based on this,although it doesn't claim to be an accurate account.
Wikipedia has an entry on Christie and a quick google showed lots of other sites if you want to follow it up.