I could see my baby cow on my phone version of the game when I got it but it became invisible a few hours ago. I don't have the problem with the leaves.
I can still see the baby cow it if I go on a neighbour visit via my other game - it really is there - it's just not displaying on the phone. I've seen this happen quite a few times before - the orphanage was invisible for a while recently, and I had big problems with the horses when they stopped being statues and were changed to animated. Sometimes the invisibility clears after closing the game and reopening it, sometimes it corrects itself and once I had to do a reinstall to make it go away. I've always thought it was something to do with my phone, so interesting to see that I'm not alone having this problem.