I can honestly tell you that even if you see a person with a striking resemblance to someone you know, it's likely not a time traveler. Think about it, Human's have around 20,000-25,000 genes with a 99.99 percent commonly shared genes. That only leaves 200-250 or so genes that really different us from one another. Whenever I factor this, it's not suprising why so many people come up to me at work asking if I'm "the son of this man, or related to this guy, or I know you, you went to my school. Wow, you look like my brother!" The fact everyone in my family looks alike, and that I look like a clone direct clone of my Grandfather... meh.... you get the idea.
So when it comes to time travel, no. It's likely a look alike. Also fashion and style has constantly been recycled since the dawn of time. Even medical breakthrough's are rehashed concepts of ancient methods of healing, such as using Honey on wounds, and leaching of the body's fluids.
But damn... it would of been awesome if there were time travels, because who wouldn't want to visit someone from the past, like meeting up with legendary figures like Peter Francisco, Marcus Crassus, or even the Greek philosophers of ol'.
Then again, time travel would doom humanity to a paradox. But it's a fictional guilty pleasure.