If a baby raccoon has been alone for more than a few hours, it may be an orphan. Mother raccoons don’t let their young out of their sight for long. Put an inverted laundry basket over the baby (with a light weight on top so they cannot push their way out) and monitor them until well into the nighttime hours (raccoons are nocturnal, so the mom should come out at night to reclaim her baby). You can also put the cub in a pet carrier and close the door. Instead of latching it, prop it closed with an angled stick. When the mother returns, she’ll run in front of the carrier, push over the stick and the door will pop open.
If the mother does not return, contact a licensed wildlife rehabilitator. In spring and summer, people often set traps in a misguided effort to resolve garbage and other “nuisance” issues. Unfortunately, this approach leads to trapped and killed mothers who leave their starving young behind. Rehabilitators are prohibited by law from accepting orphaned wildlife that are the result of human actions. If anyone in your neighborhood is setting traps, persuade them to use more humane and effective methods instead.
(Excerpted from the Humane Society)