Hire an attorney to search the Courthouse land records to verify that
a recorded easement actually exists.

Or simply go to the land records office at the court house yourself. It's
easy. I spent several summers helping my Dad by doing title searches.
Real estate law varies between states and even in different counties. There
may be other issues associated with access to public waters and lands. That
property owner may or may not have legal rights to block public access to
public property. They may WANT to do such, but that doesn't make it legal.
But it's impossible to say one way or the other without being versed in
local Nevada real estate laws and that property in particular. This would
be where, after visiting the court house and speaking with the land records
folks, that you'd probably need to retain a lawyer known to handle cases in
THAT particular county.

-Bill Kearney