Reports not displaying all information

Hi

I've noticed that when I generate a report via Accounts, Jobs, then Job Activity summary/detail, its only showing some of the expenses assigned to that job. 

We have a perpetual inventory and track our stock levels through sales and purcahses. We also rely on the use of job codes when making purchases. This is so once the job is complete we can generate a report to see exactly what expenses went into that job. 

The report, however, only displays items that were purchased that are NOT in our inventory. So items that are in our inventory are not showing on the report and therefore being forgotton. 

Is there a way around this? Or a different report option to show purchases assigned to a job regardless to whether they are in our inventory? 

Thank you 

Rebecca