But "we know that these miraculous cases do occur," adds Bozeman, "so we tailor our efforts to address the possibility. We tend to give the benefit of the doubt -- there have been lots of examples like this in other events that make us keep [hope] in mind."
Fuilla agreed that Etienne's survival was a surreal occurrence that may offer some hope -- though he said that the chances of finding someone else alive after being buried for more than two weeks are slim.
"This young girl is an exception, a miracle," he said. "But as for every earthquake, there may be people under the rubble who unfortunately die of thirst because we never locate them.
"Fifteen days after the quake, I think that it is rather extraordinary there was a miracle, but I don't believe in a second miracle."
ABC News' Christophe Schpoliansky and Lauren Cox contributed to this report.