If you log in to My Verizon you should see it. Click on "Device" (you should see this in the options below "I Want To..."
Then you will see info that looks like this:
Device Model: Apple iPhone 5 - x GB in Black
Device ID: xxxxxxxxxxxxxxxxxxx (SIM)
About My Device
Unlock SIM (PUK) Now
Click on the link under Device Actions. You will see your default pin and PUK. This is assuming that you have the iPhone 5...this doesn't appear to show for iPhone 4/4s