Do you mean to say that for an ellipted utterance such as He told me where, we can confidently assume that a question had been asked?
Not exactly. I mean that a sentence like
He told me where is grammatical only if
where is parsed as the sole remnant of an embedded question that has undergone ellipsis. Thus, I am confining my grammatical attention to the level of the sentence, making no assumptions about what has come before or what may come after. In actual usage, of course, the elliptical sentence requires an antecedent, but that needn't be supplied by a question -- e.g.:
She doesn't know where he works, but I do. He told me where.
That's interesting but where's the argument?
I had only gestured at the argument. Now I shall try to make it explicit. (I hope you enjoyed that use of "shall" as much as I did.)
1. The type of ellipsis known as sluicing only occurs with interrogative clauses, embedded or root.
2. Ipso facto, the type of ellipsis known as sluicing does not occur with free/fused relative clauses.
3. A sentence like
He told me where exhibits the type of ellipsis known as sluicing.
Therefore,
4. A sentence like
He told me where contains an interrogative clause,
not a free/fused relative clause.
Without the ellipsis (He told me where he works), we cannot make the same assumption.
Perhaps syntactic ambiguity between embedded question and free/fused relative holds in some cases with some verbs. I'm not sure whether
tell is such a verb. If, with regard to the sentence
He told me where he works, we try to interpret
where he works as an free/fused relative, it will have the value of a noun phrase like
the place. Now consider the sentence
He told me the place, which resembles the sentence
He told me his name. In each case, the noun phrase seems to stand for the answer to a question. In neither case does the sentence work like
He told me a story.