I guarantee that I have perfect eyesight, and am extremely observant, and I have paid attention to wild bees since I was a child, and that I could readily notice if any sort of sweat bee was visiting my tomato flowers regardless of how small they are. I spent days last summer watching the pollinators on tomato flowers. Sweat bees routinely visit my sunflowers, and squash, and onions, and carrots, but I have never seen one visit a tomato flower. I even know about the little worms that are around 2mm long that live inside my tomato flower's anther cones... I doubt that they are contributing to cross pollination though.
That says nothing about the rest of the world. It only means that in my garden with my varieties of tomatoes and other competing flowers, and with my species of bees, that my sweat bees are not the slightest bit interested in my tomato flowers, while at least 5 species of bumblebees were highly interested in the flowers of only two varieties of tomatoes.
I grow naturally, and never apply any type of -cide to my garden, and I actively cultivate a wide range of pollinators including sweat bees, parasitic wasps, and bumblebees.
Jeff said; "These crops are frequently visited by wild bees (halictid bees, such as sweat bees) and
bumblebees in search of pollen. This situation may contribute to a high frequency of [natural cross pollination] in bee-rich areas in crops that are primarily self-pollinated." He also said; "For example, in parts of Virginia I have observed and photographed
bumblebees (Fig. 3) and halictid bees (Fig. 4) such as sweat bees collecting pollen from tomato flowers."