If you're unable to see archived patients in your main patients list, it sounds like they're hidden from view! To fix this, head into the Patients tab, and tick the box next to Show archived patients:
This will bring any archived patients into view (they'll show up as greyed out), and you can then navigate to their details. (Also, if you tick the box, the setting will be "remembered" as you scroll through the pages, so you won't need to re-tick it, unless you actually leave the patients page and then come back later).
If you need to make someone who is archived active again, it's simple! We'll walk you through the steps here.