User didn't get logged out by autologout although it said it did.

Here's the flow of log in/out events:

1. smithj7 logged in at 7:28 am.
2. smithj7 possibly closed the browser.
3. mccanntc opened the browser at 10:28 am and typed the site and this is when smithj7 got logged out by autologout because browser was closed until then.
4. When mccanntc entered his information to log into the site, he sees smithj7 is logged in where as log shows that mccanntc logged in and then smithj7 logged in. When mccanntc logs out, smithj7 is logged out, and mccanntc has to log back in again.

This is what I have in the logs: bottom-up.

user 03/06/2014 - 10:29am Session opened for mccanntc. mccanntc (17687668)
user 03/06/2014 - 10:29am Session closed for smithj7. smithj7 (10126341)
user 03/06/2014 - 10:28am Session opened for smithj7. smithj7 (10126341)
user 03/06/2014 - 10:28am Session opened for mccanntc. mccanntc (17687668)
user 03/06/2014 - 10:28am Session automatically closed for smithj7 by autologout. smithj7 (10126341)
user 03/06/2014 - 7:28am Session opened for smithj7. smithj7 (10126341)

This is the first time it happened to my site, and I have been using autologout for 5 months. So, duplicating this issue might be tricky.