I lost my phone and want to log in from another device, but I need the verification code and don't have my phone at the moment. What can I do?
There is no possibility to log-in except recovering your password via the Forgot Password page provided by Snapchat.
Forgot password: https://accounts.snapchat.com/accounts/password_reset_request
Enter the email used on the original phone and reset the password. Try logging again and use the Recovery Code procedure to remove the current number from your phone.
Recovery Code procedure: https://support.snapchat.com/a/using-recovery-code