The SBA usually requires you to not only personally guarantee a business loan, they also require collateral from you. Title to your home, your car, all your business assets. We always joke that the SBA will take your first born child as collateral for any loan.
Even if the SBA loan is subject to a defense of the statute of limitations (for specifics, read the state law, usually posted on the state web site), they may still have the right to seize any collateral you posted to guarantee payment of the loan. Ouch!
Read your loan paperwork for the details. Hope this perspective helps!
By all means there is a statute of limitations. Check with a local attorney. Bottom line, the SBA does not have forever to effectuate a collection. If they sit on their hands and allow the statute to run they will not be able to sue you.
The SBA gaurantees the loans. They only suffer a loss when thelender sufffers a loss. Perhaps, by statisfying the loan with the bank, the SBA gauarntee was not called in by the bank so the SBA did not have to pay any money under the gaurantee.