They did 'forget' quite a lot of stuff. Things I have found so far :
The flight schedule they were supposed to take today.
The confirmation number and phone number of the shuttle which was to pick them up
One ankle high sock.
One grey teddy bear
A bunch of their food in the fridge(pineapple slice, ham, hot dogs, cherry yogurt, juicy-juice, etc)
The people downstairs will be the only ones not to miss them. They didn't much like Aiyre's running about and stomping her feet.
The apartment is much more 'homey' since they came out. Much of this has to do with the furniture Emily's parents provided(desk, dining room table, chairs, lamps). Some of it is Emily's touchs(more lamps, end table, book shelves, laundry basket)
I've not read any further in "Return of the King" since they left. Maybe I can get a couple pages done tomorrow morning before work. For those of you following along in the same printing as me, I'm on page 106, towards the bottom at the break.