X Rode in a Taxicab Driven by Y

X rode in a taxicab driven by Y. When X alighted, he left his celphone in Y's taxicab. Who owns the celphone?

A) Y is the owner under the principle of finder's keepers.
B) Y is the owner as he is in actual possession.
C) X is the owner as he was deprived of possession.
D) Y is the owner if the same is surrendered to the proper authority and the owner did not claim the same within a period of six (6) months after publication.