@SimTresaMy question is this what is the trigger for daycare, when all sims adults and teens leave the lot both the toddlers and children are supposed to go to daycare unless they have a nanny, I found that when there are toddlers in the game the children get forgotten about if the teenage sim shows up half way through. Also I was trying to figure out that problem, and its not a bug, there must be a adult or teen on the lot to take care of the children, because when I sent one of my teen and or adult sims back to the lot I got the lightning bolt icon back again. Children may be able to last longer than the toddlers alone, the lightning bolt icon not being there is the game took the children to daycare, but forgot to let the parents know. When there are only children and toddlers on the lot a popup should come up saying are you sure you want to leave the lot children and toddlers can't be left alone send them to daycare or higher a nanny.
Edit: I wish I knew how many babysitters = 1 daycare and how many toddlers and children they can have or do you need a babysitter for each age group?
I went ahead and marked it for me too I didn't even know I had the bug.