Wow, that is too bad. As others have said, it sounds like that you had a soul stone accident. When you were switching skills, you took 20 points away from blacksmithing in order to put another skill on your character. I did the same thing one time with Cartography when I was juggling skills on my many soul stones.
One thing I do now in order to make sure that I don't have soul stone accidents, is I keep all of my skills locked except the one I am taking off or putting on my character, unless of course I am currently gaining in that skill. Even if the skill is zero I lock it. Before I activate a stone, I also take a quick glance at all of my skills to make sure that I didn't accidentally leave something turned up or down the last time I used a soul stone.
Lastly, when I am working with soul stones I never talk to anyone about anything while I am working with them, and I never use a soul stone with I'm under a time deadline or in a hurry.
I'm not saying that you did any of these things, just that is what I do after having an accident similar to yours. At least, as others have said, it isn't as hard to work up blacksmithing as it used to be.
take care,
Ivy the Mage