lookup field keeps disappearing

lookup field keeps disappearing

Hi, I'm new to zoho creator and am trying to use a lookup field.  i can add the field to my form in the form designer, but when i flip over to viewing the application the lookup field is not on the form.  then when i go back to the 'edit application' mode and look at the form, the lookup field is not there either.  it's as if it is not getting saved when i leave the form.  other fields are being saved.  any ideas?  thanks in advance.