Here is a list of factual information taken from the official website of the Social Security System (SSS) for members who wants to know what to do in case they lost their SSS number or forgotten them. According to the SSS:
SSS Branches - Philippine Social Security System
Q: When a member loses the SS ID card or cannot remember the SS number, should the member secure another SS number?
A: No, the SSS number assigned to a member is the lifetime number and must always be used in all transactions with the SSS. The member should not secure another number at any other time.
If the member wishes to secure another SS ID card and cannot remember the SS number, it is advisable to inquire from the nearest SSS office.