"HERB: ...the morning he was scheduled to begin work, November 16, 1966, John Drew Barrymore disappeared, ignoring his role, his moral obligation, and his contract."
It is in accord. You can't disappear unless you have first appeared.
That's too narrow an interpretation. It's not like the studio defined the entire universe of discourse. He was out there in the world, and they'd contacted him before to arrange his guest spot. If he hadn't reported for work that morning, and they tried to locate him and there was no sign of him anywhere they looked -- if nobody, not even his agent, was able to locate him -- then it would be natural to say he had disappeared.
Besides, the first part of that sentence is the telling part. "The morning he was scheduled to begin work." Saying he disappeared in the morning means that he didn't disappear at lunch. And saying "he was scheduled to begin work" indicates that he never actually began work -- he was expected to, but didn't. The sentence is quite clearly stating that he never showed up at all.
Barrymore came in for a fitting previously but did not show up for the shooting at all: period. That is why he is said to have "disappeared" because he did show up prior to the first days filming but not ON the day of the filming.
Regarding TAF, it's def not one of my favorite episodes but as with most TOS episodes there are some cool things about it. The "only seen once" engineering section, the "only seen once" back / bottom view of the Enterprise and of course that cool ship little flying saucer looking ship with the Galileo's chair in it (and the dome that became the Gamesters habitat).