Anyway to verify SSN without W-2 or card?

My employer only prints the last 4 digits on the SSN for security purposes and does not provide copies with the full number. I also don't have/lost my SSN card long ago.

Is there no other option here that to get a replacement SSN card? I'm in my 30s and have never once had to provide documented proof of my SSN. On the Social Security website it says:

\>Many organizations can verify your Social Security number directly with us.

Why isn't Wealthfront one of them?