Okay, this is what I have found thus far. I went into my latest report from EQ and clicked on one of the accounts (any will do). In that little popup screen is the information on Worst Delinquency. Click on the "?" next to it and this is what it says:
This is the most delinquent payment reported on this account. This could extend beyond the 7 year payment history.
If you don't find this payment listed in your recent or 7 year payment histories, the impact on your score is probably minimal.