Asteroid has been given the Oumuamua and it has been classified as asteroid because it has more characteristics that resembles with asteroids than comet. An asteroid is made up of metals and rocky marerial while comets are made up of ice, dust and rocky material.
Image Credit To : ESO/M.Kornmmesser
The reason that scientist believe that it has come from two star system is because it is water less and there are only 10% chances that it could be from single star solar system.
According to the reports there are 36% of the binary stars system which can release asteroid like this one so this is confirmed by the simulation and by the logical reasoning that asteroid has come from the Two Star Solar system.