Accounts cannot be returned to a credit report after they have been taken off when the 7 year period is over. The rule of the thumb about deletion of information from a credit report is that debts and delinquent accounts get deleted from the credit report after 7 years from the date that the account was first reported late and was never again current.
If the account gets sold or transferred to a debt collection agency then the collection agency is required by the federal law to carry the original date of the delinquency when it reports the account to the credit bureau.
This ensures that the collection accounts as well as the old debt account both get deleted from the credit report after a period of 7 years. If during this period you make an attempt to contact the collection agency or make a payment towards the debt, then it does not mean that you are extending or re-setting the clock on your old debt. It will still be deleted when the 7 year period is over.
You should however remember that a collection agency may still try to collect from you even after the account is no longer present on your credit report. Different states have different laws regarding how long a collection agency can try to collect from you. This is called the statute of limitation. In order to find out more information about this, check your state laws.