Must I return the money my friend lost in a Forex company, after I advised him to invest his money in it, assuring him that it was a guaranteed company, and then its owner disappeared?

The questioner is not obligated to pay the amount or bring the person merely for consultation and urging participation, unless he has made it obligatory upon himself through a contract of guarantee or sponsorship, bearing in mind the difference in rulings regarding forex companies between what is permissible and what is forbidden.