I did hit one like that at Harrah's in Cherokee, NC a few years ago. Before they changed over to using tickets only on all the machines.
I was playing one coin at a time it the far left corner on the 50 cent machines. I was on one of my favorite 3 reel slots, Wild Cherry. I wanted to play on the machine on my left, a 5 Diamond machine, but there was a man already on it.
After about 15 minutes of playing, the man to my left had gotten up, and I didn't notice. I happened to look over and he was gone.
So, I slipped in one 50 cent coin and hit the spin button. One of the 5 Diamonds stopped on the line and the other two were just above the screen, hiding. I hit the hold on the one wild and hit spin again, thinking, "I'm not gonna hit the jackpot anyways, but what the heck".
I added another coin in the machine I was sitting at and hit spin. Before my machine stopped spinning the other machine to my left started making all of this racket. I looked over and saw, "I hit the Jackpot!"
I quickly moved over to that machine and stuck my player's card into that machines slot. Just after I had done that, I saw my wife's head peek over the macines in front of me, but she didn't see me. She was wondering who had hit the jackpot.
I stood up and said, "Hey honey! Honey, it was me!" My wife then looked up and says, "What?!" It was noisey in there because my machine was still dinging and ringing adding up the total of $750!
My wife had finally stopped playing on her machine by setting her chair up against it for a minute, and came over to see what I was talking about. She almost freaked out when she saw my smiling face and the machine I was sitting at.
That jackpot pretty much paid for our 3 day stay at Harrah's in Cherokee.