There was something on reddit last week about a bunch of folks who sold on a certain day and had double deposits made to their checking accounts. Someone from CB was saying they were going to reverse the extra deposits this week. I didn't bother to search for it now but perhaps you can find something on the topic, and perhaps it is related to your issue. Still sketchy without any notification of course. I had a buch of bitcoin go missing from my account 2 weeks ago. It took several days to hear from support but after some quick back and forth they admitted to some sort of software bug and restored the BTC back into my account.
Interesting, I'll check this to see if it's true in my case. Like most people, I'm not going over my balances with a fine tooth comb, and just accept my available balance as my real balance.
Reversing transactions though with no notice is not cool though.
EDIT: I haven't found anything on reddit yet. But I was checking the "issue tracker/operational status" thing on coinbase's page and they list no problems as having occurred. I'm still pretty upset with them. In terms of priorities, if they did double deposit people, top of their list needed to have been to inform users immediately of the situation.
