tedster - 7:57 pm on Mar 4, 2012 (gmt 0) [edited by: tedster at 4:28 pm (utc) on Mar 5, 2012]
I'm sure there are many potential loophole in WMT access - ever since they made sharing of accounts with other Google accounts possible.
I wonder, since you can't reproduce this, if someone was trying to share their account and got it wrong the first time - a simple typo, for example. They could have quickly discovered their error when the other party still couldn't see the account and then made a quick fix.
[edited by: tedster at 4:28 pm (utc) on Mar 5, 2012]