Place the baby in a box shallow enough that mother can see in and will feel comfortable approaching. It should be tall enough that the baby cannot crawl out (think shoe box size). Place a t-shirt or snag-free towel on the bottom.
Provide a source of warmth for the baby. You can use ½ -1 cup dry rice in a sock with the end tied. Microwave the sock for 30 seconds, then turn and repeat for another 30-45 seconds. Alternatively you can fill a plastic bottle with hot water (ensure the lid is closed tightly to prevent leaks). Wrap a single layer of t-shirt around the heat source so the baby isn’t burned.
Return to the exact location and watch for squirrel activity. Look in the trees for squirrel nests (called dreys): beach ball-size masses of twigs and leaves. Place the box containing the baby at the base of the tree or as high up in tree as possible
Using your smartphone or a bluetooth speaker, play baby squirrel calls for 3-5 minutes once every 15-30 minutes. Here’s an option on YouTube.
Stand vigilant from a distance. Mom needs space and sees humans as threats. Keep pets indoors and watch for potential predators.
This process may take 1 - 6 hours. Please be patient. If more than 6 hours pass, bring the squirrel inside, keep it warm, and contact the rehab for further guidance.