Losing an exam/test script is a taboo for teachers. The test is a unique piece of work done under supervised conditions and it is embarrassing for a teacher to explain how he or she lost the script.
Two decades ago when I was a rookie teacher, I actually "lost" half a script. It was a Sec 2 class and I gave them a history test. One of them, a student with special needs, asked for extra time. At that time, I did not even know there was such a concept of extra time for certain students, so I flatly rejected him.
After the class left, I checked the scripts. (I will always count before dismissing the class and count again later just to be sure) but found that only a torn script was there and another half (I think it was foolscap?) was missing! It was puzzling. I went to check but the student would not say anything. I asked a senior teacher for advice and she was quite chill about it. Just give retest..
The missing "half-script" was discovered before I left the classroom so I couldn't have lost it...what happened? My theory is that the student got angry at not being given extra time and decided not to submit the unfinished answer. But since then, whenever I counted test or exam scripts, the memory of that student is never far from my mind.