A100 point drop means that you did not miss a single payment, it means you missed entirely or made less than the required minimum monthly payment 2 months in a row. That translates to a 30 day late being reported which would be consistent with a 105 point drop in your FICO 8 score.
You can try contacting their Executive Office and pleading your case asking them to remove the 30 day late as a goodwill gesture but if their reporting was accurate the odds of your being successful are going to be quite poor. If you can show that their reporting was not accurate and you in fact did only miss 1 payment I'm sure they will correct their mistake.
Everyone else pretty much covered it.. Sorry.
I will offer this: You said it's a little used card.. Start using it- charge a couple hundred and PIF every month.
After a year of use & PIF you can try sending a bunch of good will letters to every address you can locate for them.
It may not work, but what the heck, if it does, it's far better than waiting the 7 years..
Sign up for Mint, you will be able scan through all your accounts (including investment and mortgage) and setup alerts with a single log in, I have been using it since earlier this year, along with everything being on autopay I hardly ever log into individual accounts anymore except when action is needed. Work hard but work smart.
So sorry. Yep, it’s real funky when it happens.
@along with @Oldman’s suggestion, also set reminder alerts. Hand to Gawd, I’m so worried about a mishap, I have an Outlook reminder, a bank reminder, and a CC reminder on all my CCs. It’s obsessive behavior but I too worked hard to get my scores where they are. I have autopay setup too, and I also scan my bank and CC accounts daily to ensure nothing is awry.
So get in the habit of being—well not quite as obsessive as me—overly observant.