You can run the query from the Atlassian Database Schema page to see if the data is still there:
select * from customfieldvalue where customfield=(select ID from customfield where cfname='YourFieldName');
From my testing, if I delete a value the data is immediately gone from the database so if you do find it there the first step is going to be to perform a full re-index so you'll need to schedule a maintenance period.
If you do not find the values in the database you'll need to restore from the last backup. I would also recommend opening a support ticket so the Support team can take a look at the logs and help identify what may have happened to cause this behavior and how to prevent it again in the future.
I have multiple projects that use variations of the same base workflow. The variations depend on the requirements of the project or issue type. The variations mostly come in the form of new statuses ...
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