In the past, the Family History Center Operations Guide had a guest sign-in log. The current guide does not include a form. We removed the form because centers are unique and want to record different information about guest visits.
We recommend you create your own guest sign-in page to fit the needs of your center and to collect information useful to you and your priesthood leaders. Consider the information you need when you fill out your Monthly Report as you create your page.
I serve as a Lead in my home FHC in England and have put together a bespoke Excel sheet, as an "Attendance Log".
I attach it here, for you to consider. You may want to edit it to suit your own set of information needs.
Cheerio for now!