Yep, i just did something very similar with my new Moro kris. Spunjer was there and can attest to it.
I held the sheath like i usually do and withdrew the blade, but failed to notice the opening along the seam of the sheath. Sliced my palm right open!
Then, still not realizing just how it had happened i went home and said to my wife, look honey, my new kris bite me....all i did was pull it out of the sheath like this....

.....yep, twice in one day. I figured it out after that.