Password Safe

I need to figure out the time I last used PWSafe yesterday. The "Last Accessed" value Windows Explorer was 3:43pm; same goes for the .dat file. When I was done using PWSafe a few minutes later, I closed it via the close button ("x" at top right of window). My understanding is that PWSafe -- at least, that version -- still remains in memory even after "closing" it this way. But the "Last Accessed" for the corresponding .plk file (which I gather is a lock file of some sort) was time-stamped around 5:15pm -- about the time I shut the machine down for the day.

Is it safe to say that the 5:15 on the .plk is just when the machine itself rebooted?

Thanks!