Foster lost custody of their boys Usher Raymond V, five, and Naviyd, four, last year.
But the former stylist had filed legal documents asking for an emergency hearing, just a day after Usher Jr almost drowned in a swimming pool when his hand got stuck in a drain, reported Us magazine.
However, the judge ruled in court that the children will remain in 34-year-old Usher's care.
When Foster, 42, took to the stand, she insisted her son nearly died and claimed Usher waited an hour to inform her.
Foster's 11-year-old son Kile, from a previous relationship, died last year after a Jet Ski accident.