physical volume disabled - why?

When I booted the machine today, one of the disk drives
didn't show up in the configuration. No errors in logs
that I could find. Disk Management didn't list it, but it
was marked "disabled" in the Device Manager. I enabled it
and a message popped up informing me that this usually
was caused by an error condition with the drive. I ran
all the tests and it passed. I've never seen this before.
Was it just a random Windows event or should I begin
shopping for a new drive? It's a spinning drive, not SSD,
and is four years old.