You put non-working games in "Free Play"???
How were people supposed to play them?
Should they have been in a flee market area if expo has one?
Normally the "tech" should call the number on the card to discuss you / him fixing it or getting it off the floor. Never work on someone's game without permission. It is reasonable that they plug in the cord, see it is broken and unplug it.
Free play at the 3 other shows I have been to is not the place to leave broken junk that is not playable.
Sorry I will get back to work now. I hope no damage was caused by the tech.