Final Gravity all wrong?????

So I brewed an all grain Amber batch of beer and hit my gravity dead on 1.052.  Fermented for 10 days and during fermintation went nuts. Today I kegged my brew and final gravity was 1.042???
I checked my hydrometer with water and is dead on...not sure what to do??????? What went wrong?????

Fermenting only ten points and being 1.042 would taste pretty sweet, I'd think.  How'd it taste?

If you saw active ferm for ten days, I'd suspect the hydro before the batch.  Taste should tell you something.

Still a lil sweet. I'm wondering if there is anything that I can do??? Put it back in carboy and pitch more yeast????

So I decided to transfer back in my carboy, slurried up some priming sugar and re pitch some granular yeast. The yeast I used was a smack pack and was the first and last time I use a liquid yeast. Two days of refirmiting and it going crazy. We shall see.... Cheers