The best way to recover contacts from Lg phone is with Android data recovery. It can help you recover lost notes,sms,photos,videos, and more from all kinds of Android phone. http://www.any-data-recovery.com
Did you backup your contacts before? Or do you use Gmail? You can restore the lost contacts with a backup or gmail. There are a lot of tutorials on this and here is the one that help you recover lost contacts from LG G3, which also supports other LG phone and tablets.