Vacuum over the carpet indentations. The suction from the vacuum helps restore the indentations or at least makes them less dense and easier to work with.
Loosen the carpet fibers by pressing a spoon between the carpet fibers. Work the spoon down to the backing. Pull the fibers gently with your fingers to restore their bounce. Repeat until the carpet fibers lift as much as possible.
Mist the indentations with clear water from a spray bottle. The carpet should be damp but not soaking, as this could ruin the backing.
Turn a hairdryer to medium heat and dry the carpet. Work the spoon through the carpet fibers to keep them raised. Continue until the carpet dries completely.
Repeat the process until the indentations blend with the rest of the carpet.