In file https://github.com/mozilla/pdf.js/files/5249872/product1.pdf, the fifth text widget has a default appearance using font F1 and this one is neither in DR nor in AcroForm but in AP::N::Resources.
const fieldName = [];
    if (dict.has("T")) {
      fieldName.unshift(stringToPDFString(dict.get("T")));
    }
    let loopDict = dict;
    while (loopDict.has("Parent")) {
      loopDict = loopDict.get("Parent");
      if (!isDict(loopDict)) {
        
        
        
        break;
      }
      if (loopDict.has("T")) {
        fieldName.unshift(stringToPDFString(loopDict.get("T")));
      }
    }
    return fieldName.join(".");
  }
  /**
   * Decode the given form value.
   *
   * @private
   * @memberof WidgetAnnotation
   * @param {Array<string>|Name|string} formValue - The (possibly encoded)
   *   form value.
   * @returns {Array<string>|string|null}
   */
  _decodeFormValue(formValue) {