问题中的汉语译文是错误的。

    曹老师的译文很好：I got beaned by a rock someone threw. 某人扔的石块击中了我的头。/ 我的头被某人扔的石块击中了。

    【说明】（1）someone threw 是定语从句：I got beaned by a rock someone threw.=I got beaned by a rock that/which someone threw. (that/which 是引导定语从句的关系代词，在从句中作 threw 的宾语，可以省略)；（2）rock 也可以表示“石块，小石子”。（3）bean 是及物动词，意思是：“击打（人的）头部”。