Contacts that appear as bare numbers, or do not appear at all, are almost always a sync problem rather than a lost account. The fix is to make Telegram re-read your contacts.
Android
- Update to the latest version of the app.
- Fully relaunch it: close it from the recent apps list and open it again.
- Temporarily rename the contact in your phone's contacts, adding a couple of characters, then change it back. This forces a re-sync of that entry.
- If none of that works, sign out and sign in again.
iOS
- Force quit the app and reopen it.
- Check that Telegram still has permission to read Contacts in the system settings.
- Apply the same rename-and-revert trick to the affected contact.
Before you sign out, read this
Signing out destroys every Secret Chat on that device. They are tied to the login session, not just to the handset, and nothing brings them back. Treat re-login as the last resort, and save anything you need from a Secret Chat first.
The usual underlying causes
- Contacts permission is off. Without it there is nothing to match against, and the list will stay empty.
- The number is stored in local format. Numbers saved in full international form, with the country code, match reliably.
- Duplicate entries. The same person saved twice with different formatting can produce confusing results.
- They set their privacy to restrict discovery by number, in which case nothing on your side will surface them.
Updated