No, honestly, it hasn't happened to me—even though I'm pretty careless. While my phone and PC account are both password-protected, my younger brother knows my phone's passcode, and my (+18) files are on a shared drive that anyone can open; so, it's pure luck that I haven't been found out. There were just a few close calls. Once, I was washing the dishes while listening to an (+18) audio drama CD, and my brother snatched the earphone away to see what I was listening to; the scene was right in the middle of moaning, so I grabbed it back and told him he couldn't listen because it was embarrassing—and he understood. Another instance—though not an audio drama CD—was when I wanted to listen to the Diabolik Lovers opening theme. Since I didn't have headphones, I played the song at full volume for the whole street to hear (we all know Diabolik Lovers songs feature blood-sucking sound effects).
Yes, my friends: my teenage self feared nothing.
*Whenever I listen to audio drama CDs, I always have this look on my face, but no one imagines what I'm actually listening to.*