From the reports I've seen, al Zawahiri came in with a fake passport: http://www.cnn.com/CNN/Programs/people/shows/zawahiri/profile.html
While tending to the wounded in Afghanistan, al-Zawahiri also worked to re-establish al Jihad. He eventually began traveling to broaden his network. In 1995, using an alias, al-Zawahiri even visited California on a secret fund-raising mission.
You are correct, the claim has been made that Zawahiri visited California last in 1995, not 1998 as Haaretz reports.