my entire library of photos and settings disappeared.

Lightroom or Lightroom Classic?

If Lightroom Classic:

It sounds like (accidentally) you opened the wrong catalog file. Try File->Open Recent and select each one of those catalog files until you find the one you want. If that doesn't help, then go into your operating system (Windows Explorer or Mac Finder) and search all folders on all disks for files whose name ends with .LRCAT — then double click on each one to open it in Lightroom Classic and see if it is the catalog file you want.

To get answers appropriate to you, please tell us which Lightroom App you are using and the Version Number.

Please include the following in your question:
Adobe product and Version number.
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