This issue was resolved by the card company, Elan (via Cardmember Service).
"Our records show this deposit occurred due to a customer entering their Fidelity investment account number incorrectly. We appreciate you brining this tp our attention, and are working to remove the deposit."
Wow, I thought they would at least match names for the accounts. Maybe that's only for withdrawal-enabled EFT's? Who needs passwords when misconnections are this easy?
The money is still in my account, so nothing has actually happened to fix the problem, but hopefully soon.