TLDR: A friend had only a local repository and fucked it up completly

A friend of mine had to do an project for school. Sche decided to do a little chat application. The requirements were to use java in combination of javafx.
Things started very well. Sometimes she asked me for a little help but that was no problem. She used mercurial for version control which was an inportant requirement too. But. The teacher didn't teach them how to use mercurial so all she had was a local repository. A few days ago she called me and told me that she fucked up the repository. I told her she should cerp calm and wait until i am at home. It's a fucking repository. this can be fixed i thought. But when i arrived at home and she sent me the repo i tried everything but a file (stored at .hg/store/) was missing. it was a manifest file. I asked her what happened to this file. "I deleted it because there were error messages because of it" FML. Why would you even delete such a file?
Luckily for her she sent me a copy of her repo to look at it a few days ago. so she only lost 5 commits.