I had just the opposite happen once. When I was much younger, I logged into my Ameritrade acct, which should have had about $20,000 in it, and instead it showed a balance of like -$532,000.
I nearly had a heart attack. I was worried I'd have to file bankruptcy if this didn't get corrected. Called immediately and they were super non-chalant about it. "Oh yeah, it looks like somebody shorted a fair amount of stock and it mistakenly got attributed to your account. We should get it fixed in a day or two. It's not a big deal."
I was furious and couldn't even imagine such a thing was possible. What if I had been on vacation and didn't check my account for 3-4 weeks? Would it have EVER gotten corrected, or would they have just said, "any errors need to be reported to us within two weeks, so there's nothing we can do now." Or some such nonsense.
