Claim my sketch
When collaborating on a sketch without being logged in, it somehow identifies it's always me coming back. Then, when I log in, sketchpad thinks it's another me, somehow!
In my case, it's no big deal: http://studio.sketchpad.cc/sp/pad/view/ZoErZJxyOp/rev.877
So, currently, if you're going to author some sketch, be sure to be logged in first!