That will be a coincidence. If it's the same sex then it will be an smile and you can get over it. If it's opposite sex then it will be funny for everyone and your friends will start commenting the whole day. It will be a funny day
This has always been my fear, to see someone wearing the same clothes that I am wearing at work or whenever I go outside. However, come to think of it, I think my fear is baseless and there is nothing wrong in seeing someone similar to you in terms of clothing or apparel. It is also unavoidable. The important thing is I feel comfortable in my favorite clothes and enjoying life.
I did not encounter it yet. I just remembered that I watched a movie before, where a manager track trainee was wearing the same exact outfit as what the director of the company was wearing. It was a comedy movie and it ended up to a point that her boss has to terminate her due to multiple instances of having the same clothes.