In the discussion of another sentence, a native Romanian speaker highlighted the difference between "niște" meaning "some" and "vreun" (put "vreunul", as here) which emphasises "one" (of several). Is that is correct, "Does any one of you hear me" would appear more accurate, and should at least be accepted.
Reflecting further, "vreun" appears to denote one or more individual items from a superset of countable objects, whereas "niște" denotes some aliquot of a larger volume of a substance treated as though it were a continuum. I think it's another expression of the concept underlying the distinction between "fewer" and "less".
Definitive... I don't know...
Definite... Well... "Vreunul" is an indefinite pronoun. And "vreun" is an indefinite adjective. Can an indefinite pronoun be more definite than an indefinite adjective?... Hmm.... Why not? :))) Let's say it is... An adjective can never be the subject of a sentence.