DOFD for credit reporting purposes, while often in the ballpark, is not the same as the start of legal SOL. Legal start of SOL often takes into account last account activity (ie. a purchase) and/or last payment, possibly even if it wasn't sufficient to bring the account current. The legal start of SOL likely ranges from sometime in Aug-2009 to Nov-2009...
The account agreement and judge could also play into how SOL is calculated. My layman's rule of thumb (I'm not an attorney) is SOL period + 6 months is generally safe. For example, in for MA, after 6 years and 6 months, SOL "time barred" defense should hold up well with little effort beyond asserting the defense and having documentation handy. Otherwise, if pressed, one may need to hire an attorney to argue why end of SOL should be X date, which could cost more than amount being sued for. Again, this is my layman's view; not based on any specific law nor case.
If you're corresponding with the debt collector, the odds of being sued have possibly increased dramatically. Though it depends in large part on the amount owed (under a few $K may not be worth the effort, but not an ironclad guarantee - some will sue for even very low amounts) and your current financial situation - if your scores have greatly improved and/or have applied for a mortgage lately (debt collectors watch for that), the risk goes way up.
Firstly, before researching SOL further, have you been sued? Have they merely threatened, or are there indications of a suit being filed? ... a way to tell beyond checking the courthouse is the receipt of letters from various attorneys offering to help contest a pending legal action. Often attorneys watch legal filings and get their solicitations out before the lawsuit papers are even served. If no suit has yet been filed, odds are it won't be.
Secondly, if you've saved your old statements, research the exact last activity and last payment date. Are you sure the last payment was really Oct-2009? Maybe it was a bit earlier. Can't rely on credit reporting when calculating legal start of SOL.
However, many debt collectors generally rely on credit reporting DOFD. Often this works to the debtor's benefit, such as it likely would in your situation. If this particular debt collector is relying on credit report DOFD, they likely have little to no intention of suing. Not all debt collectors include "won't sue you" blurbs, or do so very well after SOL has long since past. It's a low priority for them to do so timely.
In short, keep low and run out the clock. As of now, you may be ok, but seems too close for comfort. A few extra months would make all the difference.
