That's what kunal said. Hume to tumhe bachane aana hi tha.
Its done very cleverly. Everyone acknowledges that Abir went into the fire. However, what the brothers did was a gentleman's act, in everyone's opinion. Abir is a great actor. He is good at hiding his emotions from everyone and people are struggling to see through that.
Why mishti cares so much for kunal coming in to save her makes sense. He is her potential groom. However, why does she have no recollection of Abir... no clue. Something tells me she thinks he came for the painting.