Casino companies are not forthcoming when Hosts disappear. Yours may have retired; she may have obtained another job (casino Host or other role) at another casino; she may have been let go as part of downsizing; and so on. Casinos don't want customers following Hosts to other properties. Some may be bound by a non-disclosure agreement as to where they go. Some Hosts contact players anyway, some don't.
Send a welcoming e-mail to the new Host, you are looking forward to this new partnering, what you like, e.g. "We appreciate all that Nancy did to make our visits special over the past 15 years, and wish her well wherever the road takes us. Now we look forward to working with you! We come to Vegas X times a year, like to stay at xxx, preference is a suite in the xxx tower with a xxx view, love to eat at xxx restaurant, etc."
If you can, have a offer you'd like him/her to book for you with some or all of the mentioned preferences in the same e-mail.
Good luck.
