I had seen that before, I think, so did not watch it all the first time.
Vivaldi was never lost, as nearly every baroque composer had the printed Opus 3 and Opus 8 works, in the 1700s. There are printed copies still around, as the paper was not crap paper then. And Vivaldi in fact wrote 6 concertos with an organ part.
Nobody has written an interesting biography of Vivaldi. He left behind all those manuscripts and a bunch of begging letters to rich customers to whom he peddled concertos. There is a story that goes with Vivaldi, but it is not the story of him, but of the orphanage for which he wrote hundreds of concertos.