Empty album

Images don't disappear from Albums without a reason. Did you import old files into a new catalog thinking the Album information would transfer over?  It doesn't.  The Album information is contained within the database files and does not appear in the file's metadata.

Do you have a backup of your catalog that you could use to find the populated Album?  If so, you could:

• Place keyword tags on the Album files,
• Save the metadata to the files (Ctrl+W)
• Export those files as new using the File>Export as New File(s) menu or Ctrl+E,
• Import the new files into your catalog with the empty album and accept the option to import keyword tags. The files with the Album keyword tags will appear in the Tags Panel hierarchy under Imported Keyword tags.
• Apply the Album tag to the imported files.

An album is just a list of files referenced in your catalog. It does not contain any file, only links to the files you have added to the list. If it is empty, that's because you have not added any link. So you can add links to the album or delete the album altogether. Deleting the list does not delete any file, just like when you delete a playlist for audio files.