I don’t need to know the circumstances. Shopping carts are not meant for the safety of an infant. The part the baby was put into, is an especially not safe place for an infant of that age. A baby that cannot sit up more or less by him/herself should not ever be placed in a ahopping cart in that fashion. If the baby is put into the wagon part, he or she should be in a car seat. BUCKLED in.
Please do not cry to me about the poor tired mommy who was up all night (really – at 3-5 months most babies are sleeping pretty well at night). But even if not – I WAS that poor, tired mommy, several times over, and I never did what was described here. Either one gets a sitter, or waits for another adult to either do the shopping or take one shopping and push a stroller, or carry the baby in a Bjorn or Snugli carrier, as I did with my infants. NEVER put even soft items on top of an infant who is in a small confined space. And if a baby is crying, for Heaven’s sake TAKE CARE OF THE BABY! This is not rocket science.