Both Luke and John describe post-Resurrection encounters where the disciples didn’t recognise Jesus until they’d spoken to him, or where he didn’t look as they remembered but they somehow knew it was him. Various people have speculated about why this might be so. I wonder why Luke and John recorded it. No. That’s not quite true. I assume they recorded it because it was true. What I wonder is why people think the writers of Luke and John might have invented such an unnecessary and confusing detail. One is a skilled story-teller; the other scholarly writer. Such a narrative blunder seems highly unlikely.