Ok, so let’s say that for some reason you have a document in a SharePoint Online Team Site that aren’t being shown in search. One option you can try is to re-index the Document Library. Here’s how.
Start by navigating to the Document Library you wish to re-index. Select the COG in the top right hand corner.
From the menu that appears, select Library Settings.
Under the first column, General Settings, select Advanced Settings.
Scroll down the page that appears until you locate the Reindex Document Library button and select it.
You should now see the above dialog window. Select the Reindex Document Library.
Your Document Library will now be reindexed completely during the next indexing process at the back end of SharePoint Online. This process may take 15 – 20 minutes to full complete so be patient.
After that time period has elapsed, see whether your information is now available in search.