Can you think of anyone they may know that would have social media that you could get in touch with? they may be able to help you contact them/have a phone number?
If they have an unusual name it would be a lot easier. I think your best chance is to do an internet search.
Of course, if they have no internet presence, it would be almost impossible.
If you can't find the person directly, try finding a relative or someone they might know.