Removing the UDFs manually using the alter table command is not recommended and will not help you actually.
I believe I have seen code on internet which will take input of the UDFs you want to delete and will do all the work for you of deleting the UDFs and its references.
But since you have already rolled back the sandbox, use the code to delete the UDFs and it probably should remove all the references; if not, you might have to modify the code.
After you delete the UDFs through code, you will have to take the export of USER.xml and remove all the references of the UDFs and import it back.
This should solve your issue.
If this does not resolve your issue, please check you have entries of the UDFs in the following tables:
c. USR (per your statement, you should not have any columns in this table)
Ref : Oracle Docs/Forums.
we created 3 custom columns in the database manually using the alter table command rather than let them get created by new sandbox > Form Designer > Catalog.
Now even after adding the three UDFs from Form Designer > Catalog, and adding those UDFs to the cart page in the catalog, we see that data is not reflected from database, for the those three fields in the card details page.
There should be a file in the MDS repository that contains the metadata for the Catalog object. Remove the values that reflect the fields you don’t want anymore and also drop the columns from the catalog database table. Reimport your file for the catalog object and that should solve the issue when you go to create a new UDF. You can also check the CatalogAM.xml file that gets generated with a new sandbox and remove references.
If you just made the change, you can rollback your sandbox changes through the enterprise manager and then you would just need to drop the columns and make the first change I mentioned.