This has happened with other alphabets. Korea has an alphabetic system of writing as well as the system that uses ideographs. When I studied the Korean alphabetic system I learned of several characters that had dropped out of the Korean alphabet.
NOTE: When Iived in South Korea, the High school student must master 10,000 of the ideograph characters in order to graduate. The 24 character alphabetic system was much simpler. At one time it had 28 characters.