解釋：這裏是及物動詞hide的過去分詞，表示句子的主語I（我）是過去分詞hidden的承受者。非謂語形式。完整的句子是：As I was hidden behind the door,I wasn't found by the fellow.
翻譯：由於我藏在門後面，我沒有被那家夥發現。
提示：過去分詞作狀語，句子的主語是分詞動作的承受者；現在分詞作狀語，句子的主語是分詞動作的執行者。
例如：Waiting for a bus,I saw Jack.句子的主語I(我)是現在分詞waiting的執行者。“等公交車的時候，我看見了傑克。”這個句子等於“While I was waiting for a bus,I saw Jack.”
學習要點：英語中這幾個詞必須弄清楚：seat,hide,lose,dress,他們的句型是：seat oneself ,hide oneself ,lose oneself,dress oneself.
幫助理解：I seatd myself.=I was seated. I hid myself behide the door.=I was hidden behind the door. I lost myself in the forest.=I was lost in the forest. I dressd myself in red.=I was dressed in red.
延伸理解：As she was dressed in red,she could easily be found.=Dressed in red,she could easily be found.句子的主語she是dress動作的承受者。As she was dressed in red,=As she dressd herself in red,。