Searchable Custom HTML

I have two Custom HTML fields having the exact same piece of code and at the same position doing the exact same thing.
I have also checked all their settings and they are identical.
The only differnce is that one is searchable and on the other I don't have this option!

What is it that makes a field searchable or not?

Custom HTML fields can't be searchable. They shouldn't have a parameter to mark them searchable nor should they display in a userlists search criteria.

That sounds correct but look,



I suppose that this might be the result of a possible change in the field type?
Maybe the field was something else and then I changed it to Custom HTML, I don't remember doing this...
Anyway, what would you suggest? Should I recreate the field?

The field was likely something else before being changed to a Custom HTML field and that'd certainly cause such an issue. Shouldn't really be anything to worry about though since the Custom HTML field doesn't have any search behavior and will just be ignored on userlists.