Trying to track down paperwork for our septic - anyone been through this?

We moved into our house about three years ago, and honestly, at the time, we didn't think much about the septic tank. I mean, it was inspected and all that jazz during the sale, but we never got around to actually looking at or organizing any of the paperwork. Fast forward to now - we're thinking about doing some landscaping out back, and suddenly realized we have no clue exactly where everything underground is located. Like, I vaguely remember the inspector showing us a general area and saying "it's somewhere over here," but that's not exactly helpful when you're planning to dig up half your yard.

So yesterday I started digging through old folders and boxes in our basement storage room (you know, that place where important papers go to disappear forever). Found tons of random stuff - manuals for appliances we don't even own anymore - but nothing useful about the septic layout or permits or anything. Called up the county office today figuring they'd have something on file, but they said their records are kinda spotty before 2005 (our house was built in '98). They suggested contacting the previous owners...but honestly, that's gonna be awkward since we've never spoken since closing day.

Has anyone else had trouble tracking down these kinds of documents? Did you end up just winging it and hoping you didn't hit anything important? Or did you find some other way to get hold of accurate records without having to dig up half your property? I'm really hoping there's an easier way than playing backyard detective with a shovel...