Well some good news
Beyond astronomical odds, I find the missing tiny corner piece! Glue it back on & well it's not perfect, but better than with out it
The vendor contacts me, offers to send me a new set, (not exactly the same piece of Stab wood), if I send these back to Poland & pay 50% for the new set.
So I reply, tell Him it's not worth it & that I had found the corner spec Glued it back on & it was better than totally missing the whole corner. He refunds Me half the purchase price
So I end up with a minor flaw, but @ Half Price