Fortunately it wasn't a situation where anyone could get hurt...but I learned a very valuable lesson years ago with hand signals --
I made a slash-across-throat to someone to turn off a valve.
He did.
Unfortunately right behind him was an equipment operator who thought I was making the signal to him, and shut down the pump.
Because of a bad plumbing setup, when you did both of these things at once the hydraulics locked up. Which just meant some embarrasment in front of the class we were giving a demonstration to as we scrambled with wrenches and rags to release the pressure and get everything running again.
Now when ever I give hand signals I make sure there isn't someone else in the line-of-site who could get confused.