"Often a sentence fragment missing a verb (like this)."
English is generally "SVO" but that is largely optional. There are no rules of grammar except for the rules of grammar that are in play at a particular time. No language is a lepidopterist's fantasy of a pinned downed beauty. Language is unconstrained and free to flap its fractal wings at will.
Your "sentence fragment" is simply grammatically incorrect. You seem to have accidentally morphed "misses" into "missing". To miss is a verb. Another possibility is you might have forgotten to deploy "is" prior to "missing". Again, that is simply a grammatical faux pas and not a weird language form.
In both cases your parenthesised, aside clause, is false - t'ain't so.
That’s only intellible if I think you’re a native speaker of a pro-drop language where the copulative is dropped. Because of the structure of the English, it is ambiguous what “missing” here is appositional to, since participial forms in pro-drop languages are usually conjugated according to their case, number, and gender (at least among the Indo-European languages), so I can’t tell if the fragment is missing a sentence or if the verb is missing a fragment (or other, numerous possible interpretations).
Its not a bad thing to be wrong, since, when it comes to expression, one can never be right. But it is still better to know the best way to be wrong, a wrong way that cannot be made right. And then you yourself will have created something entirely new.
... is bollocks! Yet, I can see a shimmering phantasm of "has" ... post sentence.
If you are going to create a thing, it needs to be consistent within the framework it tries to describe itself.
A "sentence fragment", whatever that is, needs to be grammatically correct (for a given value of correct) but not simply be a spelling mistake or just plain old bollocks.
I can punch holes into a piece of A4 and call the result "a paper fragment". There is no need to define a term for "paper, useless for printing on".
That's an example of idiom. The word "what" is overloaded to mean "that is" - for dramatic emphasis.
The verb "to be" is often overloaded or implied in many languages. For example "quelle surprise" in French.
Perhaps we are dealing with a point of vocabulary. When I first learned Latin, we had "Civis Romanus" and "Mentor" as initial textbooks (kivvy was red and mental was blue). Later on a green book was added and it dealt with idiom (idia/idioms?) and I think that was its name, but I had moved on by then!
