SAN FRANCISCO -- A registered sex offender was in custody Monday after he was found over the weekend on San Francisco's famed Fisherman's Wharf with a missing 15-year-old Sacramento girl who police believe he met on a telephone party line.

Authorities said the teenager disappeared from her Sacramento home Thursday, touching off a state-wide search following the discovery in her room of the phone number of 31-year-old Anthony Butler, a registered sex offender.

The pair apparently fled Sacramento sometime over the weekend and headed to the Bay Area.

On Sunday, authorities said, the girl called her parents to report she was okay but did not want to return home immediately. She was tracked to the wharf where her uncle spotted the pair at Jones and Beach streets at 5:30 p.m. Sunday. Butler was taken into custody as a "person of interest" when police arrived.

San Francisco police Sgt. Neville Gittens said Butler was being held on two counts of having sex with a minor. The girl was taken to a local hospital for a checkup and reunited with her family.

"This is a serious wakeup call for not only my family, but any family," said Philip Watkins, the girl's uncle. "They (parents) need to be really careful with the Internet…There are guys out there pretending to be someone they are not and will destroy a family just like he did mine."