Luke 9:49 Ἀποκριθεὶς δὲ Ἰωάννης εἶπεν· ἐπιστάτα, εἴδομέν τινα ἐν τῷ ὀνόματί σου ἐκβάλλοντα δαιμόνια καὶ ἐκωλύομεν αὐτόν, ὅτι οὐκ ἀκολουθεῖ μεθ᾽ ἡμῶν. (Luk 9:49 BGT)
In context the verb Ἀποκριθεὶς carries the sense of 'responded to' or some times just to speak up (Mk 9:5; J 5:19; Ac 5:8) also according to Friberg it can be used as "as a formula to control the flow of discourse; (a) continue (MT 11.25); (b) begin, speak up (MT 14.28); (c) answer or often left untranslated"
I would suggest that in this instance Luke is recording John's response to Jesus' words without comments how good (or related) John's answer is. Responding to what another has said with something that seems relevant to us, but no one else sees the relevance is common enough in discourse.
In support of this see:
(49) Luke links the story closely to the preceding one with ἀποκριθείς.
John, as one of the leading members of the Twelve, intervenes with his
story.[Marshall, I. H. (1978). The Gospel of Luke: a commentary on the
Greek text (pp. 398–399). Exeter: Paternoster Press.]
- Master, John said, we saw a man casting out demons in your name … On the surface it might seem that between the preceding paragraph
(verses 46–48) and this one (verses 49, 50) there is no thought
connection of any kind. It has been suggested that the apostle John,
embarrassed by the implied reprimand which he and the rest of The
Twelve had received, brought up this incident concerning an exorcist
merely to change the subject. Others are of the opinion that the
insertion of the present little paragraph, not found in Matthew but
only in Mark and (abbreviated) here in Luke, was suggested by the
phrase “in my [or your] name” which occurs both in verse 48 and in
verse 49. However, another possibility must not be ignored. John’s
conscience may have been aroused by Christ’s remarks of implied
disapproval (verse 48), so that he now wondered whether he, John, and
others had behaved properly toward a certain exorcist. Whether there
is any truth in any of these guesses as to the nature of the
connection or lack of connection cannot be ascertained.[Hendriksen,
W., & Kistemaker, S. J. (1953–2001). Exposition of the Gospel
According to Luke (Vol. 11, p. 520). Grand Rapids: Baker Book House.]
Hendriksen notes some possible ways that John might have felt his comments were relevant even if they don't immediately appear so to us.