I think folks might be misinterpreting this. IANAL, so don't take me at my word, but it doesn't come down to what we think the mom was doing or what her intentions were.
You are guilty of abandoning your child according to subdivision one if (a), (b) and (c) of subdivision two are not satisfied. Meaning:
You placed your child somewhere that might be physically dangerous and without supporting care from someone else.
You placed your child somewhere somewhere safe or with an appropriate person and notified this appropriate person of where you left the child.
and, if the child is less than 30 days old (I'm not sure I understand this one.)
If I were to guess, she would be guilty of child abandonment due to violation of subdivision 2.b. She left her kid someplace suitable (safe, a LEGO store) and appropriate people (presumably the LEGO store employees can be considered this to some degree) but she did not notify them she was leaving her child behind.
Any lawyers in the house?