CA and US share their database

US to Canada: just a stamp, no database record.
Canada to China: still just a stamp, but there is a record in Airline's database. Gov. has the right to check.

china to Canada: U need to fill a form, claim customs. there is quite a lot information be recorded into CA gov's database, including your pp no.

Canada to US, your passport will be slided thru a code reader.

Sooner or later, your trip will be discovered.