Starting in 2024, Natasha Lavoie began getting calls on her cellphone from people who said they had found a missing cat named Torbo.

But Ms. Lavoie’s cat is named Mauser, and each time a call came, her black cat was where he was supposed to be, in her home in British Columbia, Canada.

This went on for a year.

Finally, about two weeks ago, she handed the phone to her partner, Jonathan McCurrach, who demanded to know why one man was calling so many times late at night.

The man admitted he was calling as a joke: His son had bought a shirt online that advertised a cash reward for a missing cat and listed a telephone number to call.

That telephone number was Ms. Lavoie’s.

Her cellphone would ring in spurts. For days in a row, she’d get multiple calls, even in the middle of the night. Then two weeks would pass without calls.

“At first I was thinking, like, who did I anger?” she said. “Who posted my number somewhere?”

She contacted the American company that sold the shirts, Wisdumb, to find out why and how it chose her phone number.