Visa requirements 180 days

I came across info on the Mexican consular site in Canada that visas are not required for 180 day stays. This has been in effect since January 2014. Why was I issued a visa upon entry by air in October?
A couple of years ago my visa went missing and I had to go through the process of getting another one. Does that still apply?
I am just a little confused as to why I was issued a visa upon entry if it no longer applies.

It's not a Visa ...... it's a tourist permit/FMM and everyone uses them

From bajabound.com:

"According to the INM (aka INAMI), an FMM, or Forma Migratoria Múltiple is an "admission document" issued to vacationing visitors of certain nationalities. Although the tourist card (FMM) is also popularly known as a tourist "visa," it is not officially a visa. U.S. and Canadian citizens driving to Mexico for vacation may obtain a tourist card (FMM) within minutes at a Mexican immigration office at the border with only a valid passport or passport card. The tourist card (FMM) may be issued for up to 180 days and is issued per person including children."

Thank you for clearing up the mud. I just finished reading "The Beast: riding the rails ..." and should know what "documented" means but now it takes on that feeling of really being documented ....without a visa. Lol.