Missing emails in Labels/folders

[iYou]

I have several emails and documents saved under numerous Labels and folders that I created and for some reason they re missing.  Any thoughts would could have happened?

[icrew]

No immediate ideas, but a couple of clarifying questions:

• Are you using the Gmail web interface, or are you using an email client (like Outlook or Thunderbird or macOS Mail)?
• Either way, when you go to the Gmail web interface, are the mails completely missing, or do they still show up when you search for them, or look for them in “All Mail”?

I’m asking to try to establish whether the messages have been deleted, or if maybe it’s just that the labels got removed from the messages for some reason….