Evidence of Time Travelers into the Past?

Anecdotally, people have found a few things from time to time that seem to imply that people from the future visited the past. An interesting example is the claim that human shoe prints are fossilized over trilobites.

Archaeologists have found what seems to be a battery in a provably ancient stratum.

I personally don't believe that time travel is possible and I don't believe it has ever happened. But that sure didn't stop me from writing a novel based on the premise. And that's because I think time travel is a deep human pre-occupation. We wish we could travel through time because as we go through life we invariably collect memories of things we botched and wish we could redo. 

My novel, In Saecula Saeculorum, describes a mission in which four young people are sent back in time to ancient Rome to retrieve information to hopefully save the modern world. 

In this novel, however, the US and UK governments that control this technology are so concerned that other countries may find out they have time travel technology, that they refuse to send anything back in time that could be found later as evidence of time travel at all.

Time travel is intriguing because we all look back on our lives and wish we had a do-over. As a personal admission, I can never forget the one that got away--the woman I should have loved more and yet so horribly wronged. I live with many regrets. But that's my journey...

Anyway, any evidence that people traveled to the past will always tug at our hearts. It will always make us wonder, what if?...