It's possible.
It's possible to save a hamster after it suffers from heatstroke, but correct first aid measures need to be taken in a timely manner.
First Aid Measures
Cooling Down: Immediately move the hamster to a cool place. You can use a fan or ice packs to help lower its body temperature, but don't let the fan blow directly on the hamster.
Replenishing Water and Salt: Dip a cotton swab into normal saline or light salt water and apply it to the hamster's mouth, or offer some salt water and glucose water.
Observing Breathing and Heartbeat: If the hamster still has breathing and a heartbeat, place it in a cool place and lower the environmental temperature as much as possible. If the hamster has already stopped breathing and its heart has stopped beating, the success rate of first aid will be relatively low.
Symptoms of Heatstroke and Prevention Methods
The symptoms of heatstroke in hamsters include listlessness, loss of appetite, unsteadiness when standing, increased body temperature, red ears and so on. The methods to prevent heatstroke include providing enough cool environments, avoiding direct sunlight, and ensuring there's enough water for the hamster to drink.
Follow-up Care
After the hamster recovers from heatstroke, you need to continue observing its condition to make sure it has fully regained its health. Providing a suitable environmental temperature and sufficient water is the key.