It is probably not stranded, or abandoned. It is likely a baby left by the adults while they hunt. In the wild, you would find entire beaches with dozens or hundreds of babies with no adults. Because they need air, the adults cannot both hunt and make sure the baby breathes.

Federal wildlife laws require that you stay back. I think 200 yards. And that might not be possible. In my town, the are often seen on the beaches right under the roads. You can be there and not see the baby seal. The interpretation is that you many not leave the roadway, walkway or bluff to get on the beach if a baby seal is present.

What happens is the adults may be watching you, and for their own safety, they do not return.