Sarcasm or Sincerity?

I had a heating oil delivery yesterday.

Below is the ticket they leave behind to show the amount and cost of the delivery.

(If you click on it, you can see a larger version in case you want to see the details.)

When I first read the "Thank you for the path" note, I couldn't decide if they were sincerely saying thank you for the path I had shoveled from the road to the front porch, which was about 90% of the way to the oil fill pipe that they needed to reach. But I had forgotten to shovel the remainder of the path (about 10-12 feet) that goes around the corner of the house to where the oil fill pipe actually is. It just didn't occur to me. 

I found a way to read the scribbled over portion of the message. After a few different unsuccessful methods, I noticed that if I held the ticket at an angle and held a magnifying glass with a flashlight shining on the scribbles..the original writing has a slightly different sheen than the scribbled part does. This was astounding breakthrough!

In any case, the scribbled over words are "to oil pipe."

So THIS becomes the interesting part. Is the first part of the message sincere? Or was it (in its original entirety) a sarcastic remark about how the path wasn't shoveled all the way to the pipe? And why is the "to oil pipe" part scribbled-over? Is it because the delivery person did, in fact, appreciate the path that lead at least to the front porch? But because the path ended 10-12 feet short of the pipe were they unable to give me full credit?
(yes, these are the things that weigh heavily upon my mind)