48kHz vs 96kHz: audible?

As a so-called audiophile, it is easy to lose one’s balance within many discussions and end up doubting, or at least questioning, whether that subtlety which one hears is real or imaginary.
 
Today, while engaged in a pastime, I was playing Holst’s "The Planets" in the background, but not at a low volume. I thought that it didn’t sound right. The strings in particular sounded a little abrasive. I noticed this on "Mars," the first composition, so it didn't take me long to perk up. On closer examination, I noticed that the DAC front panel was reporting 48kHz sample rate. I knew that this version of The Planets is 96kHz. Sure enough, JRiver Media Center (MC) was converting all PCM data (whether higher or lower) to 48kHz upon playback. I fixed the MC settings back so that all PCM rates play back at their native rates (up to the capability of my DAC), and all is well now.
 
Sometime in the recent past, whether due to an application or OS upgrade (of which there was one a few days ago), the MC sample rate conversion table got corrupted or reverted to a default configuration.
 
It would seem that I am able to hear the difference between 48kHz and 96kHz, at least under these circumstances. The difference was enough that I noticed it while passively listening (I was focused on drawing; the music was “background”) before I suspected a technical issue.

I wonder whether I could have heard this difference in a formal ABX test session? From my past experience with ABX testing, when the differences between the test objects are subtle, observations could easily have been obfuscated due to mental noise consisting of test anxiety, listening fatigue (to same passage over and over) and tedium. Whereas, in my case above, I noticed the difference when I was relaxed and focusing on something else entirely.

I am interested in thoughtful replies.