Has a ranked player ever been caught cheating during an OTB game?

In the second largest scholastic tournament in my state, there was an incident with cheating. It may seem silly to cheat in a scholastic tournament because normally the only thing at stake is a trophy, but we're fortunate in my area that one of the school systems pays to send a couple of top players and teams from the tournament to Nationals.

Many of you who played as kids know what scholastic tournaments such as these are like. The players in class C or higher generally play against sub-1200 players for the first couple of rounds and upsets are rare until the last two or three rounds. In the fourth round out of five, there were eight players still undefeated. Seven were 1400+ and the last one was in the 400s. My friends and I were a little surprised, but the only major upset he had to pull was against a 1200, which could easily be a fluke. At the time, the most we made of it was to rib the 1400 guy playing the 400 because he'd had a pretty soft schedule (playing 1200, 600, and unrated) and then along comes this 400 guy, who dropped a piece against the 1400 and gave him another easy round. After the round, I found that this 400 had been listening to an Ipod (or perhaps Mp3, I don't know) and a TD asked him to remove it for this round.

Later, the 1400 who played the 400 saw the game the 400 beat the 1200 with. His words about the game were along the lines of "He beat him with a beautiful GM-like attack". I later found that the 400's wins were wiped out - evidently the evidence was considered sufficient, although circumstantial unless the TD knew something I didn't.

Interestingly, this incident ended up benefitting me. The 1400 who easily crushed the 400 kept his win, as it was certainly too late to repair the round. This meant four players were left undefeated: a 2000, a 1600 who had taken a roughly year-long hiatus for medical issues, myself (rated at the time around 1700), and the 1400. If the 1400 had not played the 400, he might have lost or drawn and changed the pairings at the top. As it is, I played the 1400 instead of the 2000 (who I would have played if there had only been three undefeated players or the fourth undefeated player had been rated above me) and won, tying for first and guaranteeing a free trip to Nationals. The 400 has not played since, although he didn't play much to begin with.

At any rate, this makes it seem as if it's certainly possible to cheat without numerous suspicious "bathroom breaks".

I'm pretty sure lead is a metal and would only help to set the detector off 

If you want it to stop receiving signals like in your cell phone analogy, the metal detector is the thing that would have to be covered in lead (or whatever special substance you're thinking of??) ... good luck with that

Well, if too many bathroom breaks make you suspicious, there's only one way to 'cure' that - DO NOT ALLOW BATHROOM BREAKS! The players will have no choice but to relieve themselves before games and maybe try to drink less water.

I am close to coming up with a solution. by tomorrow it should be ready

Heh, ok.  Not sure how much metal is in something like an IPhone to begin with, would it set it off in the first place?  Or are we talking those wands security at an airport will wave over you?