http://www.peqtgc.com/phpBB3/viewtopic.php?f=17&t=13833

Currently one cannot interact with a trader/buyer in the bazaar if they started their trading while you were in the zone. /baz search window only shows active traders from before you zoned (trader tab), though a general search does show from all traders.
As is, if you wish to interact one needs to log or zone 1st.