In all honesty I don't think there is a simple way to get your phone back. Your mother is obviously not accepting of your sexual preferences and that sucks. I would just let her know that you being bisexual does not change who you are as a person.
I would contact some boys that go to an all boys school, they are probably in the same boat as you. Social media might be another good way to meet some guys. Go to parties and don't be afraid to mingle.
You should go for it! 4 hours away is not too bad. Just make sure to be very communicative.