Normal encounters stay for about 10 minutes if there is someone there to occupy them. If there is no one there, they will disappear. But in your case, there were pk'ers.
Uh..... I don't think they WERE pkers...... I think they only killed me in panic over my intentions, as lame a cop out as that really is...... Maybe they are, but I stumbled into their battle.... Anyways.
I understand "an event/incident/etc" remains until it's over (and now I know it lasts a few MORE minutes, so ok), but how did I get TEHRE? I should never have been able to find "there" (BUT, there is a "there" there this time, at least).....
Encounters in RT stay unless player exit it.
It was TB, they just weren't done yet.