Is there any contact information on the SD card? I found an sd card that was definitely in someone's android phone. Is there any file within the card that would have it's owner's info, so that I might contact them somehow and return what they've lost? Just going out of my way to be a good samaritan here....
Not by default, no. You can export contacts to the sdcard, but that would only contain "the owner" if they have themselves in their contacts. But you would also probably have no clue which one is them. 

While it is a grand gesture on your part, I think you are the new owner of a used sdcard.