Conventional concepts of ownership don't really apply to Bitcoin. It's just a list of messages signed with secret numbers. You can sign a new message with the old message if you have the correct secret number. The idea is the numbers are really big and hopefully impossible to guess. People ascribe concepts of materiality and ownership to these messages that aren't really true. You don't really even own the secret number. How can you own a number? You picked one at random and you hope nobody ever picks the same number.