Line of communication Puns

Back in the late 80's, my dad had a joke he loved to tell everyone he met. It went something like this:

I was driving down the road and ended up behind this ambulance with its rear door open. I tried honking and flashing my lights to get their attention about it, but they didn't seem to notice. As they turned the corner away from us, a small cooler fell out. I pulled over to rescue the cooler, and when I opened it, I found a human toe, on ice.

At this point, the victim of the joke is supposed to ask what he did with the toe. He responds with "I called the Tow Truck!" and hearty laughter.

Being the 1980's, e-mail wasn't prevalent, and calling long distance could get expensive, so he communicated with his out of state family primarily through mailed letters. He wrote this joke (sans punchline) in a letter to his mom. Not knowing it was a joke, she told the story to her friends and family. My aunt heard this story, and told it to her classes (she's a teacher) and one of her students actually got in a fight with his mom who said that could never happen.

A month or two later, we were getting together for a holiday and the toe story came up in conversation. My dad replied that he called the tow truck, and his laughter was met with horrified stares. By this time, nearly everyone in the small town was enthralled with this amazing story that my grandma had told about her son who lived in the city. She was imagining all of the people she had to contact to tell the real story to. Many took it in stride, but others were quite annoyed. Especially my aunt, who had to apologize to every one of her classes at school.

TLDR: A dad joke with no punch line doesn't belong in a letter.