To be taken away by spooks within the government such as the CIA or FBI and either secretly killed or taken to one of the secret underground prisons operated by them.
"When we last saw Jim he was attending some anti-war rally. That was 2 weeks ago. I think the government disappeared him."
A dissappearing panda is when your having sex with a girl and right after you cum you say "look a panda" and point in a different direction, quickly pull out, take off the condom and slap her in the face with it
Hey look a panda! *smack* ha they better get that dissappearing panda back to the zoo.