There have been numerous discussions about this for years. No definite conclusion of course.
The Virmire Survivor (VS) is actually one of the first to be hit by a seeker on Horizon thus being put in stasis at the very edge of the colony.
The ship seems to land at the centre of it, the spaceport I assume, so the frozen VS is quite far away from it. As Shep closes in on the laser control near the spaceport, more of the colonists have been taken then on the outskirts, where the VS must be located.
In the debrief itvis said that only 1/3 have bern taken. Lilith is one of them, because she ran into the centre of the colony.
The VS is the only one wearing armor, which can reduced the effect of tech and biotic attacks, while all others are unprotected. As both our and the collector tech is bases on the Reapers and the use of Eezo it is quite possible that the Armor accelerated the wearing off of the seekers stasis effect.
We know the VS is send to Horizon to investigate the attacks. Maybe he was prepared, as the Collectors were harvesting long before Sheps awakening. Thinking of the events of 'Paragon Lost' already happened at this point, it is not far-fetched that the Alliance Brass had the Intel aboutvthe Collector stasis and that helped the VS to overcome it's effect faster. And Horizon might also have been the last Colony to be abducted, as during ME2 we only know of Feris Fields and Freedoms Progress. After Horizon, no new abduction is mentioned on the Normandy Crew talk or in the News on the Citadel or Omega.
There are theories aswell that the seekers need close proximity to the victim and the cruiser to maintain the stasis which is controlled via a short range signal from the cruiser.
tl:dr
VS's armor reduced the stasis effect and the VS was lucky to be far away enough to be taken before Shepard arrived on on the scene.