Excerpts from Jack Boulier's message of 2018-04-11 04:25:23 +0000:
I have ubuntu xenial and koha 17.11.04. I added a new library to the database and added some books to that library. When I did a search for the text I could not find them as a superuser. The search would always query the original database and not the new branch. In the database I was able to locate the records with an SQL query. I attempted to run the koha-rebuild-zebra library attempting to get the collection updated. Now I have lost the entire collection. However the database is still complete in mariadb. Now I can not locate any items in the database.
As an experiment, try using the advanced search in the staff client (cgi-bin/koha/catalogue/search.pl). Then under the headings "Location and availability" and "Individual libraries", try selecting your new library and redoing the search. Maybe this won't help, but it would be a data point in the debugging process.