Web server, directories, is it possible to access bypassing error 403?

Question

Information Security

Good day, colleagues. Tell me
Situation - a Yandex search query led me to an xls document located at site.ru/Doc/name.xls
from a sporting interest, I drive "site.ru/Doc/" into the address bar, I get a 403 error.
The question is - how did the search engine read the documents in the closed directory?
I will assume that the search engine got to the document via a direct link, that is, the issuance of the document from the example is the result of the spider following the link directly to the document.
Question for further evaluation - how to get a list of the contents of such a closed directory?

Answer 1

the search engine has read the sitemap sitemap (any name can be set and added to the Yandex webmaster) and there is a full url to the files (with names and extensions).