Debt on credit report?

Recently i have been trying to clear my credit up. I have paid off the last of my medical bills and some hard inquiries are falling off so my score has actually risen in the last few months. I do however have two large debts that i am aware of. One is with a closed or charged off bank account totaling upwards of $3000. And another is a payday loan that is around $2000. These both date back to about 2008 but neither are actually listed on my credit report. I know these debts exist because ive called an its been confirmed, however i dont know why they are not listed. Not that i want them to be listed but i was just wondering if anybody knows why or has had a similar situation? They have both been sold to a collection company but not listed on my credit report. Any information would be appreciated. Thanks for reading.