The issue today is not so much with stronger tornadoes, as it is unlikely one of these would be missed, but more so with weak tornadoes, especially in sparsely populated areas. These weak tornadoes can go unreported because no one sees them, but in some cases they can be witnessed by many but are unable to be confirmed due to their short path lengths and relatively little damage. Take for example the tornadoes I witnessed in southern Texas on May 10th. These were the first tornadoes I ever witnessed and both were only briefly on the ground over very sparsely populated areas. Below is an image of the first tornado just north of Three Rivers, TX just as it touched down. If you look closely you can see some of the small debris of leaves and branches in the air.
This next image shows the second tornado we saw. Though it is harder to see this tornado due to our location in the storm, it did touchdown for a brief period in front of us. This tornado was also just a few miles north of Three Rivers, TX and once again only caused some damage to trees.
Despite obvious picture evidence though, these tornadoes will most likely not be confirmed by National Weather Service employees due to their lack of damage caused. This is a common problem with weak tornado confirmation and is another reason that getting an accurate count of the number of tornadoes that hit the United States each year will be next to impossible. Perhaps one day technology will advance so far that we can detect all tornadoes that occur throughout the United States but until then we are stuck with this issue in the tornado database.