Like you, i havent read the Philosophers Stone (Sorcerer's Stone in America, Philosphers here in Aus), so i'm going off memory. Its the Leaky Cauldron you're talking about, yeah? Wasn't Professor Quirrel there then with Voldemort firmly attached to the back of his head? So i'd say that yes, Voldemort was there, but not in the way you're seeing it.
Again, thats purely off memory so someone correct me if thats wrong.
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