The victim used another phone in the cellar to call for help.
The attack happened at around 2.15am on July 29. DC Jim Stephens, of Merseyside police, said: "This was a horrendous experience for the victim, who has been left extremely shaken up."
The raider is white, around 5ft 11ins, of medium build, around 16 stone, aged over 40, and with a soft Liverpool accent.
He was wearing a three quarter length black parka, with dark blue jeans and black boots.
Call police on 0151 777 4811 or Crimestoppers on 0800 555 111.