When Paineel was implimented the entire Heretic house was emptied and all that's in there now are abandoned pets. Odds are Pluxia has a nice place in Paineel now.
He is there alright, though I haven't seen him either exactly. I was walkin through tox and, lucky me, walked next to the hut he lives in. Punched me for 350 through the wall, followed up for 325 and then his pet hit me and I died. Kinda hate having things kill me I never had a chance to see, oh well.