They sold to you despite the lock so did so without DTCC involvement.
AS they did not have DTCC involvement they did not have access to the share certificates the DTCC hold to cover the trades so are obliged to hold actual physical certificates of their own to cover the trade. If they don't have those they have sold what they don't own.
Register for free to join our community of investors and share your ideas. You will also get access to streaming quotes, interactive charts, trades, portfolio, live options flow and more tools.