First of all, this did not happen in 13w09b but it does in c.
So I tried making SethBling's Useless Lever: http://www.youtube.com/watch?v=d8Etp3liY1w and when I tried to use it, the middle sticky piston disappeared right in front of my eyes!!!
MC-10915
Pistons Magically Disappear
Resolved
Duplicate
0
the1kingsam
(Unassigned)
Unconfirmed
Snapshot 13w09c
Retrieved
Duplicate of MC-9460, please use the search function to see if your bug has already been submitted. Currently over 53% of tickets are being closed as duplicate.