That old 4 hour rule has been discredited. There is bacteria on anything left out in the air the minute it gets left out. What makes you sick is not bacteria, per se, but the amount of bacteria and type. There is no general rule that fits all foods.
So your individual tolerance for bad food may also be a factor.
I did get food poisoning once, in Peru. Nasty, nasty!!
I've had it three times (never backpacking.) All three times had to do with people who did not store their food properly before serving--once in Peru. once in Italy, and once right here in the good ol' USA.
Nasty doesn't come close to describing it.