A highly-infectious 32-year-old woman and eight-year-old girl sparked a nationwide alert by absconding together from the clinic on the outskirts of the capital Freetown on Saturday.
The pair, who are not related, were tracked down at an undisclosed location in the evening and returned to the clinic after radio appeals were made to the public, the National Ebola Response Centre told reporters in Freetown.
"Our contact tracers and surveillance officers are meanwhile tracking the level of contacts the two would have made during the period of their escape," a spokesman said.
Sierra Leone has seen almost half of the total caseload, reporting 3,941 deaths as of Wednesday last week, and is currently treating 10 patients.
More From This Section
The World Health Organization (WHO) reported in June that a retreat of the virus "that was apparent throughout April and early May has stalled" in Sierra Leone.
President Ernest Bai Koroma announced in early June he was imposing curfews in the worst-hit parts of the northwestern districts of Kambia and Port Loko.
The curfews had been due to end earlier this month but have been extended indefinitely.