The `/tmp` directory is delibery cleared by the operating system when booting and in the case of some operating systems also every few days. Geany cannot control the operating system behaviour, so files can disappear from `/tmp` in operating system removal. That is what it is intended for so that all the temporary files will be removed and the directory will not grow unacceptable large.

If your file isn't a temporary do not save it in the `/tmp` directory. You can set it somewhere else by setting the `Plugin Manager->Save Actions->Instance Save->Directory to save files in`. Note that the entry has a note that `/tmp` is the default and there is a note that if the files are saved elsewhere then the directory will continue to grow in size and you will have to manually clear it as the operating system won't clear it.

There is some alternative features in the save actions plugin #3911, but it is not merged, but you can try it. And even if it is merged for the next Geany version so far there is no documents so nobody will know about it.