Baby pigeon fell out of his nest? What should I do?

I hope you read Sarah's answer and did what she suggested with the exception of the dog/cat food. That baby needs a baby bird formula mix from the pet store and you use an oral feeding syringe. Birds have little sense of smell and touching him makes no difference to the mother. It would be great if you could find the nest, but since you can't, you can feed him. Just be careful and let him have some control so that you don't put food down his airway.