The only opportunity to cancel a send like this is if your campaign had send throttling enabled. You will have to look in the User-Initiated sends folder for your email. If not all the emails have been sent the status of the email will be in progress and you can pause or cancel the send via normal Salesforce Marketing Cloud Procedures.

1. Click Tracking
2. Click Sends
3. Click on the email
4. Click on Cancel send or Pause send