Galaxy S5 mini - Locked and I don't know the alternate password
I don't know if this works or not, but according to this post:


  just unlock it via findmymobile.samsung.com
  you either need to already have an account there or just setup one.
  you can simply unlock it via this service.


Since it's an official Samsung service instead of a sketchy third-party one, it seems like it's worth a try. I don't think it will work though, unless if you've already set up a Samsung account on your phone and given it remote access.