我误拿了别人的书。

I picked up someone else's book ___by ___mistake.

我误付了这笔账单两次。

I've paid this bill twice ___by ___mistake.

30分钟后，一个男人出现告诉我们他误拿了我们的行李箱。

After 30 minutes, a man appeared telling us that he had taken our suitcases ___by ___mistake.