Salmonella is an infection strictly speaking, not a toxin. Although it is often acquired from food, it is not a normal constituent of most foods. It is a normal constituent of some feces i. e. the feces excreted from an infected individual or animal. The typical pattern in adult infections is stool contamination of food > sufficient time and growing conditions to reach an infectious amount of the bacteria > ingestion of the contaminated food by the victim > sufficient time to produce an amount of the bacteria to cause symptoms in the victim (typically including diarrhea) > passage of infected feces by the victim and so on. So yes, some people are quite resistant to certain strains of the bacteria, and can clear the bacteria from their bodies. Some people are immune to the effects of the bacterial toxin that causes the symptoms and can harbor the bacteria in large numbers without becoming ill, and still pass on symptomatic infections from their stool (carrier state). Since heat kills the bacteria, adequately cooked food renders it harmless. And the bacteria do not grow well in the cold, so cold storage keeps the numbers low in contaminated food. And if the food is not contaminated by the bacteria, then any amount of poor storage or preparation of the food will not cause it to harbor the bacteria.
It is also possible to acquire the bacteria directly from the source instead of via the intermediary of food. So watch where you put your mouth.