Identifying the User Who Changes Part Status in Windchill ---- LastModief and ModifiedBy problem

I am retrieving the following data from Windchill's PTC.ProdMgmt.GetValidStateTransitions() API:
"Items": [
{
"Value": "INWORK",
"Display": "In Work"
},
{
"Value": "RELEASED",
"Display": "Released"
},
{
"Value": "CANCELLED",
"Display": "Canceled"
}
]
We use these values to indicate the status of a part. If the part is ongoing, it is "In Work"; if it is canceled, it is "Canceled"; and if it is completed, it is "Released". The main problem here is that we cannot find the user who logged into Windchill and selected one of these statuses for the part. When we make such changes, the Modifier API does not show the information of the person who made the change. How can we identify the user who made this change?