Recently installed a 15 x 30 above ground. In a rather large rain storm, some of the inside cove sand washed away and I have a low spot inside the pool near the wall. Is there anything I can use to fill this low spot without draining 10,000 gallons?

Not really, anything that can fill there low spot must also lift the weight of that 10,000gallons of water. Sand is a poor cove materials to start with as you have found. Expanded styrofoam strips work well but that requires dumping the water too.