Donatello knocks Shredder's helmet off his head using his staff and the helmet lands on the ground. Then when Blodgett drives the news van into water, he finds the helmet on the wooden dock.
When Shredder is complaining to Baxter about his helmet missing and is about to send him out to find it, his face mask is tied around his face from behind. Later when he recovers his helmet from Baxter, the mask doesn't have a knot nor support on the back of his head to hold the mask.
Whenever the helmet with the Eye is removed from Shredder or Baxter, everything they created or transformed into either disappears or changed back into its original state. But when Baxter takes the helmet from Blodgett, the comic books Blodgett created didn't turn back into his sofa.