Drupal 7

In D7, if you delete a field from a content type, the field data stays in the database. And yet if you later add that same field back to that same content type, the data does not reappear. Zuh?

It’s the new deleted field in each field_data_<field_name> table that governs this behavior. So if you accidentally delete a field and want that data back, just change the deleted field from 1 to 0.

Kinda cool I guess, though it sort of reminds me of the trash can in WordPress. As far as I can tell, though, there’s no UI for adding back deleted fields.