Can I file I485 when my J1 Waiver is approved but without USCIS Approval Notice?

I obtained a Favorable Recommendation for my J1 Waiver from the Department of State (I received a letter from DOS regarding this) and the case was sent to USCIS. I received a Receipt Notice from USCIS for form I612. The Case Status Online only shows that “Case Was Received At Another USCIS Office” but when I called USCIS, they said that the case was approved and the Approval Notice was sent. However, I never received the Approval Notice letter in mail. Can I go ahead with filing I485 without the Approval Notice from USCIS (only with the letter from DOS) and the fact that the Case Status Online is not updated? Are they going to issue an RFE while the case is approved in their internal system? If yes, what should I do without the Approval Notice?