Missing swap file since latest update- Sierra
In previous versions of OS X I always had at least one swapfile. That never went 'away'. Regardless of how much RAM was available.

But since Mavericks the memory management improved steadily (including zram-like vm-compression) and on the latest macOS after a fresh reboot I also do not see a swapfile. It gets then created as needed. 

Only if you have low amounts of RAM in the machine and never see such a file created is there a reason for concern. 

If you open a few apps and then Safari with a few tabs filled you shall see those files again.