The proliferation of smartphones and social networking applications has led to the emergence of mobile forensics as a critical field of digital investigation. Snapchat, in particular, poses unique challenges for forensic analysts due to its ephemeral nature, disappearing messages, and encrypted storage. This study presents a systematic forensic investigation of Snapchat artefacts across iOS and Android devices, utilizing a controlled experimental design and an array of specialized forensic tools, including Magnet AXIOM and Cellebrite. Through simulated user activities such as messaging, calling, media sharing, and story posting, followed by logical, filesystem, and memory acquisition techniques, this study identifies key artefacts that persist despite Snapchat's emphasis on privacy. The results indicate that on iOS devices, identifiable metadata, including installation information, unique identifiers, and structured database records, are recoverable, alongside communication and media artefacts. On Android devices, investigators recovered installation metadata, chat and memory artefacts, multimedia content, and session tokens. A cross-platform comparison revealed similarities, such as SQLite-based history files, as well as platform-specific differences, including iOS reliance on PLIST configuration files and Android dependence on token-based authentication storage. The findings of this study underscore that Snapchat, despite its ephemeral nature, leaves behind substantial traces that are accessible through forensic methods. These findings have significant implications for law enforcement, security professionals, and researchers addressing cybercrime, harassment, and data leakage. The study acknowledges limitations, including hashed passcodes and fragmented artefacts, which highlight ongoing challenges in the field. Future research should focus on expanding the scope to newer Snapchat versions, encrypted backups, and cloud-synchronized data.