Logged back in and all previous data gone

What kind of account were you using on the old phone? If you had a subscription account then all that data should have automatically downloaded to the new phone, provided you logged in using the same account credentials that were used on the old phone. If the data has not downloaded, login to the account at lightroom.adobe.com in any browser to verify the contents of your cloud account.

However, if you were using the free version of Lightroom on the old phone, then you need to be aware that cloud syncing is not available in the free version. If the old phone cannot be accessed, the only way to get your data back is if you happen to have a backup of that phone, which the new phone is able to access, e.g. via an iCloud backup in the case of iPhones.