Two Errors Lumped Into One - File Field Deleted - Cannot Be Found/Deleted/Recreated
You should, in theory, be able to just remove the references to that field from the field_config and field_config_instance tables, clear caches, and then be able to recreate the field again as if it never existed. 

Please do try that in a development environment first; it's also possible, in theory, that some other non-core module has a reference to that field in some way, which may either be responsible for the problem in the first place, or cause problems when you manually remove the data.