Trouble with F4 Help on 1 Field

I have a screen where several fields have dropdowns for a selection of valid values;  however, 1 user cannot see the list of valid values for one of the fields.  He can see the dropdowns for all the other fields, and all other users can see the list of values for the particular field he is having an issue with. I am wondering if he accidentally created a personal list with no values;  however, when clicking on the F4 help, no window appears to even try to delete such a personal list - I'm not sure if this is even the issue?  Has anybody ever seen this before?  Any help with clearing this up would be appreciated!