Heh, that reminds me. I was at the lfs the other day looking at kribs, and there was this thing I assumed was a rock. I didn't really look at it and didn't pay any attention. Then all of a sudden I realized it was a 14" pleco! So, yeah, they're good at hiding, lol. And yeah, it looks like you've got a pretty big tank and lots of hiding spots, so it isn't unreasonable that you didn't see your plec for 6 mo. Heck, I loose my 2 L387s in their 16g tank. And it's a tall tank, so there really isn't much bottom space for them to be in. But, there are lots of hiding spots. Don't worry, btw, mine are moving into their new 75g home soon. They are only about 2" each right now.