A reader reminds us that the correct word is "unfazed." As for Spock, one might say he was "unphased" when a Klingon took his weapon. But when writing about how Spock reacted to being disarmed, the word is "unfazed."

What does unphased mean?

Adjective. unphased (comparative more unphased, superlative most unphased) Not phased; not organized or structured in chronological phases. Misconstruction of unfazed.

Is it not phased or unphased?

Not phased. Common misconstruction of unfazed.