I've used that yeast strain before for a couple of lagers. I fermented at the top of the yeast's recommended temp range. I did a yeast starter. I had no problems.
Whenever I use a new strain of yeast I check out the company's info on the strain. You are at the very bottom of that yeast's recommended temp range. Since you didn't do a starter you did underpitch. Those yeasties are a bit overwhelmed right now and since you took the temp down to the bottom of the range they likely flocculated out.
I agree with a prior poster that you should get the temp up to the upper part of the strain's recommended range. Don't forget to swirl the fermenter to rouse the yeast. You might need to rouse them once or twice a day until fermentation is cranking.
It will work out. :-)