For "reasons unknown", Walter Koenig, the actor who played Pavel Chekov in "Star Trek", and his wife left the Vancouver studio prior to a scheduled appearance on CNN's Larry King Live where they were due to make an appeal for their missing son Andrew.

The 41-year-old Growing Pains star who suffers from depression went missing on Valentines Day in the Vancouver area and has not been seen or heard from since.

Speaking on air Larry King said, "For some reason unknown to anyone, Walter Koenig, the father of the missing Andrew Koenig, and (Andrew's mother) Judy Levin-Koenig...left the studio in Vancouver." He was unable to offer an explanation for their leaving. "We checked them out, they were prepared to go on, I said 'hello,' they said 'hello.' We said we'd be on in two minutes, they said 'fine.' And they got up and left, for reasons unknown."

Andrew Koenig's sister Danielle appeared on Larry King Live last night to discuss her brother's disappearance. "It's just very upsetting," she said. "My brother does suffer from depression, so we're very, very worried about him, and we just want to find him."

Earlier this week, Walter Koenig made an impassioned plea to find his son. Speaking at a news conference in Vancouver Koenig said, "I implore, I beseech, I humbly request that even during this extraordinary time, when you have the Olympics here and there's so much going on, if the population can take one more step and try to be aware that we have a son, Andrew Koenig, who is presently missing, whose state of emotional health may not be very good...just look out for him."

Police say Andrew Koenig was last seen in Vancouver on February 14 and was due back in Los Angeles two days later but never showed up. Since then, police have canvassed the man's friends and searched Vancouver's sprawling Stanley Park, one of his favorite spots in the city, but so far haven't discovered anything which might reveal his whereabouts. Koenig's cellphone has not been used since February 16, according to authorities, and he last accessed his bank account a few days before that.