Many Banns registers have not survived. Checking records for St Thomas, Exeter on Findmypast they do not list a Banns Register covering 1833.

I would check with Devon Heritage Centre to see if they hold a Banns register for St Thomas.

Unless there is an error on the marriage entry I would say that the marriage took place after Banns were called.

Marriage Allegations & Bonds to obtain a marriage licence are held at Devon Heritage Centre with images of some available on FamilySearch.