TikTok does not keep deleted DMs retrievable in the app — once you delete a message it is removed from the thread for both sides, and the recipient cannot recover it from TikTok's interface. But there are three places a copy can still exist, and they are worth checking in this order.
1. Your own data download. In TikTok: Profile > Menu > Settings and privacy > Account > Download your data. Request the JSON or TXT export. It includes your direct messages as they existed when the export was generated — useful if the deletion happened recently, patchy if the thread was old, and it only covers your account, not the other person's.
2. Notifications and email copies. If message notifications were on, the notification history on the phone can contain message previews — on Android, Settings > Notifications > Notification history; on iPhone, the Notification Centre if the alerts were never cleared. If email notifications were enabled, the inbox has the text.
3. Device backups. An iCloud or Google backup made before the deletion still holds the app's data, and restoring that backup to a spare device can surface the old thread. This is the only route that reliably recovers a full conversation, and it requires a backup that predates the delete.
What does not work: third-party "TikTok message recovery" sites. TikTok's messages are stored server-side under the account, and no external service can query them. Those sites collect logins.
For parents, the practical point is that deletion is normal teenage behaviour and chasing deleted DMs is a losing game — the durable approach is supervision at the account level (TikTok's Family Pairing lets you set screen time, restrict DMs to friends, and filter content) plus device-level visibility where it is lawful. On Android, Windows and Mac, Ultimate Phone Spy captures message and app activity as it happens (parental control features), which is more useful than forensics after the fact.