Lucky Thirteenth?

I'm not sure the reasons behind it, but there was an old family friend named Amos who once went through a spell where he needed many surgeries. For whatever other reasons of which I am also unsure, me Pops ended up the contact person for him. Amos had no children and what family he had were all living in Kentucky.
I should mention here that Amos was extremely, indeed fervently, superstitious.
One day during the course of all Amos' health issues he had to have a surgery fast. It was a we need to know this instant, don't dwell on the answer, we'll lose him if don't operate immediately situations. Yet Amos himself was in a coma and could offer no instructions. Pops happened to be in the hospital and was approached about what to do. Operate, he of course told the doctors.
The surgery was done, and Amos came out in flying colors.
Well past any danger a couple of weeks later, Amos still lay in the hospital recuperating. Me Pops went to pay a visit. As they talked, Pops could see that Amos was calculating. Eventually he asked, in a fit of pique, "That was my thirteenth operation. Why'd you let them do it?" he demanded of Pops.
"What was I supposed to do?" Dad responded incredulously.
"When was the surgery?" Amos then demanded.
"I dunno. Two Fridays ago I guess."
"That was the Thirteenth!" Amos exclaimed. "You let them operate on me for the thirteenth time on Friday the 13th?"
"You made it, didn't you?" Dad said with a wave of his hands. But I suppose when superstition gets a hold on you, it grabs tight.