That's why my suggestion was to trap the ladybugs inside a "cage" WITH the aphids.they just didn't want to stay, all the aphids are still there
It generally works better when the ladybugs come to your garden voluntarily. Conscripted ones may be disoriented or may not be familiar with local aphids, or they have other things on their tiny little minds. They sometimes sell pheromones/bait to entice the ladybugs to stay.