On my first kerballed mission to Minmus, I landed and sent Jebediah out on EVA. After climbing a mountain and then returning to the ship, he was almost out of jetpack fuel, at which point I realized I had neglected to include a ladder on the ship. So, after several failed attempts to get him into the capsule, he was completely out of jetpack fuel. I decided to send a rescue mission to pick him up. When the rescue mission arrived, Jeb's ship was still there, but Jeb was nowhere to be found. Only afterwards did I realize I had stupidly clicked "End Flight" instead of "Space Center", thus condemning poor Jeb to non-existence.