Steam Guardian only seems to discount the cost of a fire spell that gets drawn , but not the ones currently in your hand ?
It reduces the cost of ONE fire spell in your hand, not ALL of them.
The draw happens first, before the cost reduction. So if it happens to draw a fire spell, it could randomly choose that one to reduce the cost instead of some other fire spell that was already in your hand.
Sounds like that’s exactly what happened. It drew a fire spell, then reduced the cost of that same spell.
So, it seems like the card did exactly what it was supposed to do.
What actual bug are you reporting?