The sole purpose of getting another Solgaleo/Lunaala is to trade with someone who have an extra Solgaleo/Lunaala like I did with my big bro.
If you don't want to, better Wonder Trade it on an actual console. XD
Here's the daily Island Scans(Once per day):
http://www.serebii.net/sunmoon/dailyevent.shtml
If you have 100% Island Scan cheat, you can easily found all 4 in one day.
BTW. I already Wonder Trade Unova Starters on Moon.
The purpose of scanning QR Code is to register a Pokemon. Even if you haven't caught it, it will identify as "haven't caught".