Growing up, my mother always kept her tomatoes on the window sill, but her ketchup in the fridge. I figured this was just because there was usually not enough room in the refrigerator to put the tomatoes. However it turns out that there may be an actual scientific reason for this than just hear-say.
Apparently, its be known for a while that putting tomatoes in the refrigerator takes away its flavor, even though technically they are kept fresher longer when refrigerated. Yet scientists did not know the mechanism behind it.
Basically if a tomatoes is kept under a certain temperature (68 degrees Fahrenheit) the genes that give the tomato its distinct flavor shut down. Once these genes are off they can not be turned back on. So unfortunately if you make the mistake of putting the tomatoes in the fridge, you can still eat them, but they won’t taste right. Source
According to The Post harvest Technology Center at US Davis, If a tomato is stored at under 50 degrees it wont only change the flavor but give it a mealy texture as well. Source
So basically, always keep your tomatoes at room temperature, unless you want a mushy tasteless fruit on your sandwich. If you do make the mistake of reinvigorating your tomatoes, use them for marinara sauce.