o passports get stamped when flying from the U.S. to Canada? I'm considering a trip but I do not want a record of it on my passport. The last time I drove to Canada, my passport was not stamped, but I would rather fly. I asked google, and it sounded like the passport might or might not get stamped.

Google is right.  They may or may not do it.  Aside from Canada, when you fly home, you have that same situation again with US customs.  Sometimes they don't stamp, sometimes they do stamp.  I have seen them do it both ways with my US passport, whenever I return home from another country.   I am talking only about going through customs at an airport.  Both the US and Canada never stamped anything in my passport, ever, when I have driven back and forth, and I have done that dozens of times.

flying in and out of Canada on a weekly basis and my passport was stamped every time ...

Are you concerned about a visible-to-the-eye stamp that you don't want a friend or relative to see? Or are you talking about a government record of your travel from Canada?  

"The U.S. Passport Card can be used to enter the United States from Canada, Mexico, the Caribbean, and Bermuda at land border crossings or sea ports-of-entry and is more convenient and less expensive than a passport book.  The passport card cannot be used for international travel by air."

I have flown to Europe and not had my passport stamped... and other times it was.  I doubt if you can know for certain.