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.
this.data.fieldValue = this.data.buttonValue = null;
    
    
    const fieldParent = params.dict.get("Parent");
    if (isDict(fieldParent)) {
      this.parent = params.dict.getRaw("Parent");
      const fieldParentValue = fieldParent.get("V");
      if (isName(fieldParentValue)) {
        this.data.fieldValue = this._decodeFormValue(fieldParentValue);
      }
    }
    
    const appearanceStates = params.dict.get("AP");
    if (!isDict(appearanceStates)) {
      return;
    }
    const normalAppearance = appearanceStates.get("N");
    if (!isDict(normalAppearance)) {
      return;
    }
    for (const key of normalAppearance.getKeys()) {