I'd almost worry about the lettuce washed in the tap water more than the under-cooked beef. Buffets are like Petri dishes for food poisoning and with air temps between 80? and 100?, the conditions are optimal in the Tropics. Hot foods should be no less than 135? after being fully cooked (usually to 150?, 165? for chicken) and cold foods should be no more than 40?. Imported ground beef should be safe above 135?(med rare), but I wouldn't trust any ground beef processed in the DR to less than 155?(med well)
As for "being sure," that's why institutional kitchens in the US keep records of food temps from start to finish. They document the cooler temps at least twice a day, temp the food when it's first cooked, and then again when it's in the buffet at least once an hour.
It could have been food poisoning, but without tests, it could have just as well have been Norovirus, which is spread by hand and surface contact. You can get that just by touching a doorknob or stair railing and it's very common in resorts and cruise ships.
personal hygiene is very poor.......amongst catering staff and managerial staff who think they are above it all.
you really do take your life in your hands when eating from a buffet., wait for new tray to come out is one idea......
I have worked for years in places where people have sniffles and don't wash their hands when toughing their face. its a problem.