IT DEPENDS ON THE STATE.  Here in Michigan, the burden is on the owner of the real property to be sure anything that affects the property is recorded at the register of deeds, and this includes probate documents.  No independent abstractor searches other courts in Michigan.  And the bankruptcy system is so weird, we've no way of knowing what district a bankruptcy is IN so even bankruptcy searches are not done by abstractors.  All of us here have disclaimers on our forms and I always make sure out of state clients know that we don't search other courts.  (All liens are recorded at the Reg. of Deeds, too.)

 I believe a lot of 1 owner searches in other states are being performed with a "no other courts" disclaimer in order to compete with the overseas contingent.  Since most title companies (and/or underwriters) get credit reports, those same big companies seem to be accepting work which most of you in other states would consider unfinished.