Can I retrieve the phone number (or recording) of an incoming call I answered, but didn't attach to a lead?
When you have an incoming call from an unknown number and you answer the call, there are buttons "Create new lead" and "Assign to lead" while you're on the call.
If you miss the call, it appears as a "Missed Call" record in your Inbox where you can easily call back or create a lead from the missed call record.
If you answer the call but didn't attach the call to a lead during the call, you'll see a "Call from unknown number" in your Inbox with a duration (and recording, if available). From there you can easily call the number back, create a lead from the missed call record, or assign the call to an existing lead.