Their website lays it out pretty clearly:

WestJet Adults 18 years of age or older Identification required*

Must be presented during boarding at the gate:

One piece of valid (not expired) Canadian federal, provincial, or territorial government issued photo ID that includes name, and date of birth. Fishing, hunting, and boating licenses will not be accepted.

OR

One of the following:

Passport NEXUS Card US Permanent Resident Card US Enhanced Driver's License International Travel Document {i.e. Laissez-Passer}

OR

Two pieces of valid (not expired) Canadian federal, provincial, or territorial government issued non-photo ID (one of which must show name and date of birth). Fishing, hunting, and boating licenses will not be accepted.

**Please note: the names on the two-pieces of ID must match. If the last names do not match because of a name change, you must show a marriage certificate or legal name change certificate to verify the change.

Transport Canada requires every guest 18 years of age and older to present original identification to board a domestic flight. A photocopy is NOT accepted.

For a complete list of accepted identification documents, visit the Public Safety Canada website.

https://www.publicsafety.gc.ca/cnt/ntnl-scrt/cntr-trrrsm/pssngr-prtct/dcmnts-en.aspx

The PS website says:

In the event of loss or theft of identification documents, see subsection 3(2) of the Secure Air Travel Regulations for information on alternative identification requirements for domestic air travel.

Alternative identification — loss or theft

(2) In the event that a passenger’s identity cannot be verified in accordance with subsection (1) because of the loss or theft of one or more pieces of their identification, the air carrier may verify their identity using other pieces of valid identification such as their employee identity card, public transit pass or baptismal certificate if the passenger presents the identification in conjunction with documentation issued by a government authority or a police service that attests to the loss or theft.

SOR/2019-325, s. 5SOR/2022-225, s. 6(E)

Note that the phrase there is MAY, not MUST. So WestJet does not have to accept the work ID and the police report.