Most people think that animals, including cats, don't have long-term memories. They think that an animal's memory only lasts for a short time after the event occurred. However, there is some evidence to suggest that animals do have long-term memories and can remember past trauma.
One study found that when cats were re-exposed to a traumatic event (in this case, being placed in a room with a predator), they showed signs of stress and fear. This suggests that they remembered the previous experience and were scared of it happening again.
Other studies have shown that animals can remember specific events from their past, such as where they lived or who their previous owner was. So it's possible that cats could remember past trauma, although we don't know for sure.
If your cat has experienced something traumatic, it's important to be aware that they may be feeling scared or anxious about it. Try to create a calm and safe environment for them, and if possible, avoid anything that could trigger their memories of the event.