Contact a buyer who commented?

HI folks, I made a mistake on a video I have for sale where my file does not have an alpha channel… a customer pointed this out to me today and I’ve re exported the video with an alpha channel, they said they need it today but are not responding to my reply under their comment in the product comments section. I’ve looked at their profile but don’t see a contact option. Any ideas how I can get the corrected version to them? Thanks… also can I replace my main file in my product page or do I need to delete and re-upload the product for review again?