The 21-year-old unnamed woman approached a passerby in Stirlingshire in central Scotland in distress after her escape two weeks ago, the Glasgow-based Daily Record reported Monday.
She told police that she managed to escape from her captors in an unspecified location, before making her way to the town.
Police suspected that the woman might have come from north of Stirlingshire, possibly the rural Tayside area.
"At the moment, we are continuing to liaise with the young woman as to her ordeal and try to establish a more definitive location as to where she has fled from,” inspector Nigel Thacker was quoted as saying.
Scotland reported 213 suspected trafficking cases last year, with about half of all potential victims coming from Vietnam - by far the main country of origin, Reuters reported.
Many young Vietnamese have made tortuous journeys through Russia and Europe, having paid thousands of pounds for the promise of a decent job in Britain. But the truth is they often end up enslaved in nail bars and cannabis farms, or forced to sell sex, the report said.
In January, members of a gang who forced Vietnamese girls and women into slavery in nail bars in Britain were jailed for a total of nine years.