I would say "You found it." and I think most Americans would say that. British English uses the present perfect tense in cases where American English would use the simple past tense.

The difference between "You found it." and "You have found it." is the same difference there is between "Mario arrived home." and "Mario has arrived home." If I say "Mario arrived home." I am not saying where Mario is in this moment, while when I say "Mario has arrived home." I am saying "Mario arrived home, and he is still at home."

I would say "You found it." and I think most Americans would say that. British English uses the present perfect tense in cases where American English would use the simple past tense.

The difference between "You found it." and "You have found it." is the same difference there is between "Mario arrived home." and "Mario has arrived home." If I say "Mario arrived home." I am not saying where Mario is in this moment, while when I say "Mario has arrived home." I am saying "Mario arrived home; he is still at home."