A no ball is when the bowler steps over the popping crease. Also a no ball can be when a bowler balls a bowl a full toss which is higher than the waist hieght. Is case of a no ball the batsmen cannot be caught, LBW, hit wicket, stumped or hit wicket.
However, he can still be dismissed for a run out, handling the ball, hitting the ball twice, or obstructing the field. - (from Wikipedia)
If the umpire thinks the batsman was trying to run, when the 'keeper collected the ball & dismantled the wicket, it could be considered a run out, not a stumping and hence he could be given out.
Source - Wikipedia