want to know where the sales text is available in sap

Hi Gurus,

Need help on below query. The Invoice is created with sales document as PO.

We know Text is picking from STXH/STXL table by executing READ_TEXT Function module and passing to idoc segment. What we is dont understand is where this particular text is available in the screen level and in which tcode. We have searched in material text/PO text/delivery Text/sales text also. Still no clue. Please help on this.

Values passes to READ_TEXT FM are in the attached image. Name is the Billing invoice along with item number combination.