Read-only form value not submitted

(Apologies if this is being posted in the wrong part of the community - I couldn't see anything about OAF form personalization so Oracle Forms was the closest I could find.)

I'm trying to do some basic personalization of a page which is an HTML form in the E-Business Suite (version 12.1.3) - which always seems to mean problems compared with personalization in the Java-based Forms.

All I want to do is fill in and lock down one particular field's value, to restrict what users of a particular responsibility can search for through the form. Easy enough in Forms but OAF is behaving weirdly.