How can I erase my data if my phone doesn't show on Find My and the screen is unresponsive?

I recently dropped my phone and cracked the screen pretty badly. I have AppleCare+ so I ordered a replacement phone for $99. The replacement phone arrived and I was able to do my transfer, however the screen for my original device became unresponsive before I could erase the phone.

Things to note:

1. In order to begin the transfer, I had to turn Find My off on the original device, so I am not able to remotely erase it via iCloud.
2. I called Apple Support and they were not able to do anything remotely.
3. I made a Genius Bar appointment and went in person. They plugged the original device into a Macbook for 20 minutes and said they wiped my data. However, when I look on my Apple ID, the old device still shows (and even had my credit card still linked via Apple Pay, which indicates to me that the original device was NOT erased)

Is there anything else I can do to ensure my data is erased? I have to send my original device back and would like to know that my information is safe before I do so.