I did another test and the first thing I noticed was when you pick up the basin with the baby in build mode there isn't actually an option on screen to put it in the inventory. So maybe I was wrong and you're not actually supposed to be able to put babies in there and it's just a glitch that you can do it with backspace. Anyway, this time I had the baby stuck on fine and after about half a day I was warned about the baby starving, but then nothing more happened. I watched the baby for two in game days, but it didn't disappear and I didn't get any more warnings, and as far as I could tell the other sims in the household ignored the baby completely. I probably should have tried to watch it a bit loner, but I'm tired and not really in the mood right now.
