I operated QF21 on the 19th
Was it the 19th you travelled on the 21 ?
I operated on the NRT 4 day trip. Every NRT trip has over 200 Japanese school kids at the back for the last 4 weeks,
L4 is the CSS jump seat, so I can't imagine the CSS not noticing you, during the flight on the 19th I made my way through the cabin to the back at least 10 times during the dead of night. That was me with my torch dodging feet in the isle.
Sorry but some pax require sleeping time at 2 or 3 am EST, departure is 2215 from memory so we tend to make it dark as possible and patrol the cabin every few minutes, maybe some one cut you some slack for a little stretch break and some comfort.