If you still can't find the kittens after all this time, then mama probably hid them where you wouldn't be able to get at them anyhow. The last litter that I rescued was hidden in an empty covered swimming pool. The cover had been nailed down with a tin cover and I have no idea how she even got in there in the first place. It was weeks before she brought them out. When I was finally able to get my hands on them, their eyes were crusted shut and I had to put salve in their eyes. Mama cleans their eyes and my vet said that's the best treatment for it but in this case, it wasn't, so you might want to watch for that. My vet said that, if I hadn't put the salve in their eyes, chances are they would've gone blind. Mama didn't want to leave my front porch, so I assumed they were nearby but they weren't. It wasn't until I began walking the property and when I got near the pool, she got nervous. So I stopped and listened and sure enough, they were in there. Mama knew how to keep them safe.