You've gotten me curious, Rana, did they change the title of one of the books for the stateside market?
I remember the Philosopher's Stone being a concept of alchemy, a stone that would help in changing base metals (lead, etc.) into gold. It was sought for with the same fervor (and same results--never found) as the Holy Grail.
A "Sorceror's Stone" would just be a rock owned by a wizard--no particular meaning beyond the literal.
If I'm not mistaken in my understanding of the two phrases, it would seem rather, well, stupid to substitute one for the other.