Yes, I have noticed this as well.  I used to fish in BB floating wreckage, and I would zone and go from runecloth bolts to mageweave almost everytime.  I was so pissed (after losing a RARE pattern) that I reported it, the GM's response was "that is not possible".  So yea, for those of you who have something good in there, I would reccommend looting asap.