It can be a picture of something the mistake led to, or just a picture of the mistake.
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So Last Week One Of My Friends Blackmailed Me Into Giving Him My Locker Combination.
I was out sick today and I was sent this picture. He apparently broke into my locker and put the lock on the little hook thingy, then left. He and I are the only ones that know my combination, so none of my other friends could do anhthing. One of my other friends made a "lock" out of notebook paper "so nobody could break into it". So basically this is a mistake because I was stupid and gave him my actual combination and now I'm going to go through this stuff for the next week and however long I keep the lock.