Are you using a form button to submit the recipients details? If so, the form button is designed to always write to a new row. If you want to edit an existing record, you need to enable editing and click on the pencil at the top right of the screen to edit the record. Or you need to add entry fields on the detail screen.
If you still prefer to use a form button, then you will need to also write some sort of unique identifying information from the item detail you are viewing. The form will need to write to it’s own separate sheet. In the data tab you will then need to create a relation column to link the item to the item in the form response sheet. Then create lookup columns that use the relation to pull back any data you need from the form sheet into the item sheet.