Great question, @Emily_Porter! Figuring out where a person has been for care is very difficult. And it's something that we haven't tackled effectively yet. Insurance companies will know which offices/doctors have submitted claims for a given patient, assuming you haven't switched insurance. And some e-prescription companies will be able to get a list of prescribers for you. But neither make that information readily available.
I've found that most doctors/hospitals keep records for 7-10 years (though some much longer), and we've made a policy that actually refunds users for requests where their records weren't found. But it'd certainly be great if we could figure out upfront which offices had a record for a given patient without having to request from many.