These hearts are almost never anything permanent.
I find them, take a picture and let them go on their way. This has been happening to me for twelve years. I don't know why this happens and I don't want to know. I like to think that it is a reminder that everything is ok, that love is always on my side.
That someone loves me and they are thinking about me ~ that is what these hearts mean to me.
I hope you find your own hearts, wherever you may go. Hearts abound!