Contacts lost on iPhone 17 after iOS 26.2.1 update

When contacts seem to disappear in iOS it is almost always simply due to either one of your Contact accounts not being logged in as it was prior to the update. Once the account is logged in again, the contacts will become available again.

Because Contacts are typically stored on a server that is also associated with an email account, the first thing to try is to check Mail for all of your accounts. Fetching email may prompt you to log back into the account that is having the problem and thereby solve your Contacts problem.

If that doesn't work, check the accounts listed in: Settings > Apps > Contacts > Contacts Accounts

If the account (usually an email provider) is not listed in there then use "Add Account" to add it back. If the account where you store your contacts is listed, then tap it, and ensure that "Contacts" is toggled to the ON position.