I'm pretty sure that resetting sync history doesn't actually remove anything, but forces iTunes to compare the local library with the device and copy over anything in the current sync selection that isn't there. I'd liken it to clearing your web cache. That said I don't have access to the code, so I'm making some assumptions.
I'm not entirely certain what the deal is with voice memos. They used to sync with iTunes, but I'm pretty sure Apple switched them into a cloud only feature, although it might be one of those legacy things that only changed if you agreed to a prompt at some point. I know mine go via the cloud and sync to the voice memos app on my Mac. I'd have to check exactly what happens on Windows. I guess what matters is do you have copies of the files on your computer, and do the ones on the phone work? If there is anything important do you at least have a backup.
tt2