I went ahead and sent AS a note, framing it as a safety concern (which it is) and certainly not asking for miles/compensation (which would seem strange IMO).
If I had to speculate, I would guess that the FA was tired/distracted and simply overlooked it. This was the last SEA-PDX shuttle of the night and I heard the FA's talking about how tired they were and how this day was even longer than yesterday. There were a good 20 minutes sitting at the gate after boarding had completed and prior to pushing back, during which the FAs were all upfront chatting, including an FA deadheading in F.