There could be many reasons why a document disappeared for no reason while reading a novel on a phone. The following are some possible reasons: 1. Phone memory card damaged: If the phone memory card is damaged, it may cause file loss. It is recommended to replace the memory card or use the built-in storage space of the phone. 2. Mobile phone software problems: Some mobile phone software may malfunction or lose files, especially when using the mobile phone to read novels. You can try uninstalling the software and reinstalling it or try to view the novel in another application. 3. Phone System Failure: If the phone system fails, the files may be lost. You can try to restart the phone or try to run it in safe mode. 4. The file itself is damaged: If the file itself is damaged, the file cannot be used even if it is copied to another location. It is recommended to download the file again or read the damaged file. If the file disappears for no reason, it is recommended to try to download the file from another source or contact the phone manufacturer or software developer for help.