Hi Soumya
I am sure you would have checked this already, but is it that the Substitute is also getting the work item ... not as a substitute but as an actual agent?
In cases where the Actual Agent is person X and there is a substitute Y for that X -> we see the name of X in ""substitute for" field. However, if the Actual Agents are X and Y (Both), even if substitution is there, it will not show the name of X.
regards,
Modak