Dude, he was either messing with you, or he was misinformed himself.
You can tell if it were either a sativa or an indica after it starts to grow, the leaves are different, as well as the growth patterns, indicas are more prone to being short, along with a shorter growth cycle too.
As far as guessing the exact strain, I'm afraid your out of luck.
Peace.
one of my friends pointed to a seed in my bag and said that that was a skunk seed this seed was i looked like it was flater than the others but theres more seeds like this in the bag