I already have a hyphenated variant, but would like the non-hyphenated version too, for a slightly better user experience.

I'm happy to make an offer to buy the domain from the current owner.

The whois gives me contact details for them, but the email address bounces, the registered company doesn't appear to exist (at least, any more), and the phone number goes to a voicemail message that sounds like a pocketdial.

Short of driving up there (about 100 miles) and knocking their front door, I'm wondering what else I can do.

The domain was renewed earlier this year (and is one of 70 or so others, I gather), so I'm guessing it's someone who bought and didn't use it, or who is deliberately keeping it to sell on, but if no one can contact them, that's a bit of a problem...

Any suggestions, beyond me getting in the car?