The Purchase by Vendor report does not show all Vendor Bills.
The Purchase by Vendor Summary and Purchase by Vendor Detail reports are designed to display Vendor Bills posting to Asset and Expense account types, including subtypes: Other Current Assets, Other Expense, etc.
A Vendor Bill may not be available in the report if the related Item or Expense is posting on an Account other than those mentioned above. Please see steps below to check:
Open the Vendor Bill record in view mode
Click GL Impact subtab
Note: Account in Debit side should be an account with Asset or Expense account type