(Initially it was a guess, but then @tivnet found a proof from US speaker)
My guess is that the word сайт (site) was used "as is" in Russian-speaking Canadian community before it was borrowed in Russian language and become widely accepted word. I mean that it was used as "purely English" word that has no Russian counterpart (like "Я вчера на сейле купил большой пэк пива с большим дискаунтом!".
So, it could be used as a shorter word than "домашняя страница" (or "веб-страница") which was used in 1990-ies and the feminine gender sticked to it at those times. Now when "сайт" is accepted in Russian, the feminine form already existed and continues to be used though "сайт" become a masculine word.
Now when @tivnet have found a proof I will cite the US poster.
The original post contained the following line:
Сайт не велика по объёму, но сделана с любовью и функциональна.
The poster later describes why he used feminine gender:
когда я использовал слово "сайт", я имел в виду его перевод на русский язык - "страница", которое женского рода. А что, существует сегодня такое самостоятельное слово в русском языке - "сайт" ? В моё время, 13 лет назад, его не было. Также как "юзер" (по русски - пользователь) и массу других слов. Когда я использовал слово "сайт - я думал, что это обыкновенное жаргонное загрязнение, но я при этом не один и не первый !
alemo - Май 06, 2004
(Note that 13 years before 2004 is 1991)
Here you can see that many people use "сайт" as English word and they don't even know that Russian language has already included it in its vocabulary. I think this is very similar to your Canadian friends who left the Russia before сайт become a Russian word.
I've read somewhere that when people cannot recall the proper word they nevertheless can describe the word's gender, and many other characteristics but not the word itself. For example, talking about traffic accident the speaker can forget the proper word for a car, but finds it just when the word is needed:
Я не заметил эту... - как это по-русски?.. - car.
Here "Car" sounds masculine, but in fact it just substitutes the proper word - машина, which is feminine. So all the words in the sentence support the feminine gender, while the used word doesn't sounds the proper way.
Still sounds weird to me: "Как тебе моя новая сайт?" :-)
– tivnet May 04 '14 at 17:36