It says I already have an account, but I never made one

If you've ever started a booking or a listing with this email address, an account exists — even if you never finished. Signing up again won't create a second one and won't send you anything.

Go to the login page and use “Forgot your password?”. That gets you into the existing account, with anything you'd already saved still there.

If the address genuinely isn't yours, ignore it — nobody can use an account without access to the inbox.