The raid, led by Cotabato City Mayor Muslimin Sema, the MNLFs secretary-general, was carried out with the help of local officials, the police and the Armys 6th Infantry Division.
"We found (the kidnappers) hideout but they had left even before we could reach the area," Sema told The STAR.
Car dealer Norman Sia was snatched here last month by three men while road-testing a Kia Pride he was selling to them.
Sema said Sias captors have fled deeper into the Liguasan Marsh, a 220,000-hectare delta at the boundary of Maguindanao, Sultan Kudarat and North Cotabato.
He said they are certain that the kidnappers had lookouts on the routes leading to their hideout in a marshy district in Talitay, where they kept Sia captive.
Preachers of different evangelical groups here, led by Troy Cordero, appealed to the city government last Monday to help secure the release of Sia.
Earlier, the military pursued Sias captors at the boundary of Talitay and Datu Piang towns, but intruded into an MILF enclave there, thus triggering three days of hostilities which left more than a dozen soldiers killed.
Four soldiers were captured during the firefight, but MILF rebels later released them in response to an appeal from Lt. Gen. Rodolfo Garcia, Armed Forces vice chief and chairman of the governments ceasefire committee.
The rebels also nearly shot down a military chopper ferrying troops to the area from their command base in nearby Datu Odin Sinsuat town.
Garcias MILF counterpart, Datu Benjie Midtimbang, said their forces in the area are now working with the MNLF and local leaders to rescue Sia from his captors.
Sema said the conditions at the raided hideout of Sias captors were "miserable."
"There is no source of potable water there. There is no electricity, and mosquitoes are everywhere," he said.