I assume you looked at the log file and didn't see anything to cause the park command to be sent?
I'm pretty sure I wasn't doing anything on the laptop when the mount parked either night (in fact I think I was napping the first night), but I have to admit I wasn't paying attention so anything's possible. I will be more aware next time.
Would it be possible to add an entry to the log file when someone does something to park the mount, especially when double clicking on the status bar? If I accidently cause the mount to park in the future it would be obvious in the log file.