On this day i did leave to go with a pt who was going for an endoscopy, that was not assigned to me, I did ask her( the pt ) where she was going and also asked if she minded if i go with her... She stated that, " that would be great " so i did give report on my assigned pt to another student because i could not find my instructor Karen Costigan . On giving report to fellow student they said she had been gone for awhile and had no idea where she was, but she was nowhere on the unit. I understand to NEVER leave the unit without the Instructors permission and will never do so again.