Rob Lowe is suing his former nanny for violating a confidentiality agreement. The nanny, Jessica Gibson, countersued Rob and his wife Sheryl for sexual harassment, and a second former nanny joined by also filing a sexual harassment suit. Apparently the confidentiality agreement, that Jessica claims she never signed, has gone M.I.A. A dismissal motion has been filed on Jessica's behalf that says, "In effect, Ms. Gibson has been sued for breach of a nonexistent contract." Lowe's attorneys only said, "We'll be responding to this in court, which is the appropriate way." A source close to the Lowe family said, "Everyone who works for Rob knows that confidentiality agreements must be signed. There are plenty people who can verify that Jessica signed one. But after her employment ended, the papers went missing." The next hearing is scheduled for June 19. Photos: WENN ...