When a rabbit gets bred multiple times, sometimes that creates kits at different times, which means they stay at different stages of development while inside the doe. Usually when the first set of kits is born, that expells ALL the kits. When that happens, the premature ones usually die. But obviously sometimes when the first set of kits is born, the rest stay in utero and are born later at their normal birth time.
Also, first-time mothers often have no clue how to care for their kits. Most of the time those does figure it out with their second litter and do fine from then on.
A good mother rabbit will pull fur from her belly and use it in a pile of straw to create a nest. She will have the babies in the nest, and clean them up. Then she will completely ignore them, returning to the nest only one or two times every 24 hours to nurse them. You are likely to never see her near the kits or the nest. That's normal.
If this mom did not nurse her kits within 24 hours after birth, then you were right to foster the kits to a different doe.
If you think there might still be more kits, then give the doe a nestbox and keep checking, you might be able to catch the newborns before too much time has passed and get them fostered out too.
Hope that helps!
