No, he has been on there since the day of the trade. And online team rosters mean nothing, they are entirely unofficial. Just whatever the webmaster or PR department choses.
I'm not sure refusing to show up for a physical is the same as failing a physical, is it?
Seems like the League would want to take a stand on that one. Richard Seymour wasn't traded - his contract was. And his contract is currently owned by the Raiders. If he legitimately fails his physical that's one thing but I don't think the League is going to allow a defacto "no trade clause" in every contract because a player might not want to play somewhere
Seymours only option then would be not to play - but I can't see the league handcuffing teams by giving in to this tactic