Disconnect the lines! I had a pitot/static test done (that IFR test)
a couple years ago and the moron didn't understand how to do it (a
student learning under the direction of the A&P who was someplace
else) and cost me $3K to replace/repair and re-install everything.
And since I can't prove it, my loss.

As for keeping this from happening again...the classic tennis ball
solution -- slice it open about an inch, slip over the pitot tube.