Ringgroup and managing not answered calls

I’ve a Ringgroup with 3 extension. 2 extensions are usually in the office and the third extension only in the morning. the third extension is working from home after lunch.

Following problem:
External call → ringgroup no answer
On every phone (mobile or softphone) the unanswered call is listed
Extension 1 calls the customer back
Extension 3 calls the same customer back when he has time

The problem is, the no extension knows which missed call who has called back.

How to handle that?