Just Used Ult W and flash on trist

W + Flash give a combined 1300 distance (for comparison, fog of war starts at 1100 distance away). R provides 600/800/1000 knockback distance; assuming you were above level 16 this makes a combined gap of 2300 units (slightly over 2 entire screens of distance). At this point the only reason Vayne could catch you is you used flash and W two feet away and then ulted a random minion instead of Vayne.