The last time was in a diner and I ordered sliced tomatoes as a substitue for hash browns with my omelette. I knew something was wrong by the time I got to the parking lot. I spent the next 24-48 hours dealing with nausea and diarrhea. I'm thinking the sliced tomatoes had to have been sitting out there a long time.
Another gross thing is the fruit they have at bars, like the sliced lemons and limes that they put on the rim of your drinks. Unless you know for a fact that the citrus is freshly sliced, stay away from that too.
Its always about the omelette not the tomatoes. The omelette has bacteria built in and isn’t heated enough to kill it. It would be cardboard if it was. And, you’d have to take a dump on the sliced tomatoes to get anything nasty from them.