This happened to me to just a few days ago I'm like what the hell I tried adding up my credit cards to that amount no luck and I'm trying to figure this out myself but it did bring up my credit score by 11 points like you said no info what-so-ever if you figure it out please let me know, thats how I got on this was trying to search it on the internet, Thanks.
Try contacting the credit bureaus directly and ask where they got their information from. Someone reported the account, so see if they will provide the information that got it on to your report in the first place.
If the bureaus don't have any information - dispute the account. If the bureasu can't prove the validity of it and if you legitimately have no record of it, then it doesn't need to be on your report. If the bureaus can't verify it, they will remove it.