Wow, if they in fact removed you got really lucky. Most people here have no success with GW's to Capital One. I have been trying for about 6 months, granted I'm trying to have them remove the entire tradeline. Congrats, hopefully they have requested removal of the 30 day late from all 3.
The fact that the OP had a payment returned here makes the situation quite different than a standard GW adjustment request and IMO greatly magnifies the chances of success here.
OP, I'd suggest starting a thread in the rebuilding section if you want more replies and feedback on this.
Can you send me the e-mail you used for the CEO? I am in the same situation. I changed banks in October of 2018 and didn’t switch my autopay over to my new bank in time which caused Cap One to try to take it from old account. The payment was returned and now I have a 30 day late. Once I realized it, I changed the autopay to new account and have been on time since, and I’m hoping they’ll remove it since I’ve never been late (the only card I have no lates on) and it’s been open since 2013.