Your general question generally has to do with copyright law. If you had the arrangement as a work for hire wherein you hired this person to take photos, then they are your photos and if you specifically indicated this is your work and your friend does not own the copyright, then they are your photos. However, if you did not have this arrangement, you will probably need to go to court to force the photographer to release said photos to you. Further, depending on the type of arrangement, your signature on a model release form is not indicative that you own the copyright unless all parties signed on to this.