Most newer vehicles don't come with block heaters installed, so unless you've had one installed it's fairly likely that there is no block heater if you can't find a cord.
Alternatively, you could examine the oil pan for a missing cord. If you purchased the car used the previous owner may have had one installed and broke or lost the cord. I had a 2001 Saturn sedan a while back that the block heater cord had been cut off by something the previous owner had hit, I just had to buy a replacement cord and the broken one simply unplugged from the heater on the bottom of the oil pan.
Finally, if your car is having a hard time turning over you could try switching weights of oil in the winter. I used to run 10W30 in the summer months and in the fall switch to 5W30. Or you could use a synthetic blend or full synthetic motor oil. If you don't know much about lubricants I would suggest looking into them before you do this, just to make sure it won't cause any engine harm.
I was recently browsing some forums that I read and someone mentioned something about a magnetic block heater. Apparently JC Whitney sells this model and you can just attach it to your oil pan for heat.