Who, etc. - Zion’s joyful wonder at the unexpected restoration of the ten tribes. Secondarily, the accession of spiritual Israelites to the mother church of Jerusalem from the Gentiles is meant. This created surprise at first (Act 10:45; Act 14:27; Act 15:3, Act 15:4).
lost ... am desolate, a captive, and removing to and fro - rather, “bereaved of ... have been barren, an exile and outcast” [Horsley]. She had been “put away” by Jehovah, her husband (Isa 50:1); hence her wonder at the children begotten to her.