Isn’t a word missing?
You are right: it is a simple error. The writer forgot a verb like said or added or something similar.
Yeah, I definitely think this is a typo or a simple mistake, we need a verb there.
said
stated
asserted
Something to that effect.
Indeed; a word is missing. The missing word may be completely intentional. Sometimes a writer will omit words in order to make identification of their own work simple in a situation where it is copied and pasted without attribution.