This only covers time travelers from the future. If one were to use similar methods to find time travelers from the past, we'd probably find millions of candidates :)
Travel to the future is actually more probable(theoretically possible), I am basing this on a good explanation by Brian Cox(based on Einstein's theory of special relativity).
The basic premise is that to travel to the future an object would need to reach near the speed of light, the closer you get to the speed the further you can travel into the future, but travelling back would not be possible.
A direct quote from Brian Cox "If you go fast, your clock runs slow relative to people who are still. As you approach the speed of light, your clock runs so slow you could come back 10,000 years in the future".
