I think they are only there part of the time, although I'm not exactly sure what the schedule is.
They were gone previously as well several times that I did trade runs, but they were back just last week or the week before. I remember reading something on the Korean boards about possibly changing the gold exchange traders to certain days of the week, but I'm not sure what came of that.
Sorry I can't be more definitive. :/ My best advice would be to just check out one of the trade-in areas before you make/move your package and see if she's around that day. If not, just wait till later.