btw, I am assuming Allan38103 is also a MEM flyer, maybe he took your seat
The 38103 certainly made me think he might be from MEM, but I wasn't sure when his "Location" said otherwise. Maybe he did take my seat.

In all honesty, that would be so rich to catch a poacher in the "wild" of FT.
well, it was certainly possible that 18A would show up after me. I am usually the last to board but I'm not necessarily boarding as the are closing the door.
Assuming you would ask for a switch or quickly move had 18A arrived, not just pointed out where 18A could otherwise sit after being woken from your headphone covered fake sleep, then I would call your move seat "exploring."
Seat Exploring: Exploring an otherwise unoccupied seat when it
reasonably appears all surrounding seats have been settled to determine if you would like to inhabit said seat in the event it has no indigenous people or other rightful occupant(s).