Do not assume the referral disappears just because the employee later leaves. If it was already submitted, the application record may still retain it.

The exact mechanics depend on the firm's recruiting system, and a referral is only one part of the application anyway. Trying to replace it immediately can create unnecessary duplicate outreach.

If the referral was submitted and you received confirmation that your application entered the process, the employee's later departure does not necessarily undo that history. Recruiting can confirm if you are unsure.

Keep the original confirmation, continue with the application, and contact recruiting only if you have a specific reason to believe the referral is missing. Do not chase a second referral just to replace the first one. If useful, this guide on consulting referrals gives more detail.

I doubt the referral just vanishes because they left afterward.

Would only bother recruiting if you have a reason to think it isn't attached.