The woman, 21, was subjected to a serious sexual assault on Eyre Place in Edinburgh at about 4am on Wednesday.
Police said they have now traced the good samaritan who came to the victim’s aid.
They are still trying to trace a man described as of Asian appearance, aged 20 to 30, with short dark hair.
He was smartly dressed, wearing a blazer, and may have left in a silver car.
They would also like to speak to any taxi drivers who may have been in the area.
Detective Inspector Keith Fairbairn said: “I’d like to thank all those who came forward with information but our appeal to the public is ongoing.
“We are very keen to speak to any taxi drivers that may have been in the area of Eyre Place Edinburgh between 3am and 4am on the morning of Wednesday October 8”.