Actually, in addition to that format being used for "homemade" boats, it is also used on boats built prior to the November 1972 USCG required HIN. If you see a HIN that has a "Z" as the 3rd character, it indicates the HIN is State-Issued, not Manufacturer issued. Some staes do use a date in the HIN based on the original; build date of the boat, others use the year that the HIN was assigned to the boat.
Since 1989 an official HIN has been required by all States in order to officially sell/buy any boat and it is definitely needed when registering the boat with the State. The State-issued HIN is SUPPOSED to be "permanently" marked on the outside of the transom, near the starboard side, and also in an additional "hidden" location known only to the owner (or builder). That said, not all boatowners actually do mark the HIN on the boat, but should as it could mean a lot of help identifying the boat if the boat were ever lost or stolen.
Original Hull Identification Number definitely was NOT ever lost "to the sands of time", since htere never was an original HIN on this boat. O'DAY ID'd every boat built prior to the 1972 HIN Requirement with 2 numbers on a little metal plate (and it does appear that that little metal plate may have been lost?) Anyway, those 2 numbers (as pictured in my original reply) would be a "HULL#" and a "CLASS#", Hull# refered to the total number of boats built by O'DAY up to that time, and Class# refers to the total number of that class, in this case Day Sailer. As an example: my old Widgeon was Hull# 22698 and Class# 1791. That means she was the 22698th O'DAY built and the 1791st Widgeon. (Somehow, when I registered my Widgeon in December 1988 I was able to use 226981791 as the HIN, should not have worked, but it did!)
So, yes, this State-issued HIN was assigned to the boat due to there not being an original HIN, but it is the OFFICIAL HIN now.