The little girl with the scar on her face
Why didn't anyone miss her?
shareHer mom was too busy with baseball...
sharePennywise had an effect on adults that made them "allow" things to happen. Just look at how many times adults did actually see something, but then just turned away.
shareAs AtomicX said, Pennywise mentally distracted the mother and everyone else who would've seen her go under the bleachers.