Am I about to be ripped off?

So, I ordered some pizza earlier and I paid with my VISA (it was online ordering). The pizza got here about 8 minutes late so my friends and I bitched and moaned until we got it for free when the delivery guy came. He did not look very happy when he left, anyway... we got free credit for next time instead of a refund since I paid online through credit card...

On the receipt that the delivery guy took back, I didn't give him any tips but I left the "gratuity" section blank, meaning he could potentially write like... some random $$$ onto it and collect!

If he does, I plan to collect free pizza's for the rest of my life when I sue !!!

Sir, you are eating something that was thousands of years in the making.  You are not being trash; you are being a man of the future, enjoying his futuristic nourishment.