Summary:
If ראובן bought the field with אחריות he cannot retain the money if זקפן עליו במלוה, but he can retain the money if לא זקפן עליו במלוה. However if שמעון bought the field שלא באחריות he can never retain the money (even if לא זקפן עליו במלוה).
I am indebted to your father’s creditor because of Rabi Noson - משתעבדנא לבעל חוב דאבוכון מדרבי נתן
Summary:
Only by a שעבוד of קרקע can it be considered transferred to the creditor’s creditor (since the middle creditor can always collect this קרקע), but not by מטלטלין (since the middle creditor cannot collect these מטלטלין if his debtor sold them)