I just tried this
@echo off
findstr /c "Justicar Aatrox" elophant.txt
if %errorlevel%==1 (
echo Justicar Aatrox >> skinsNotOwned.txt
) else (
echo Justicar Aatrox >> skinsOwned.txt
)
which returned the same results. Clearly the problem is in the way I search. I think it is searching for any part of the string. So if I had another string with Aatrox in it or Justicar in it, it would return true.