Those chips are nothing more than clay with numbers printed on them. No way they will be able to track down and invalidate that many chips. Not possible. That $1.5M in chips is a free pass to gamble til your heart's desire. Not only does the Bellagio not have any way to track them, nor does any of the other casinos that would accept them at their tables which happens quite often in Vegas. The robber may not be able to trade them 1:1 for cash, but 1:1 for other casino's chips is where he'll see a return on his theft. $10k here, $20k there, nobody will ever flinch at someone having that much in chips. Especially from the Bellagio.
$10k here, $20k there at a time... you're not going to get to wear your motorcycle helmet while cashing them in, or trading them for other casino's chips. 1.55 mil is 155 10k's. Let's say you have 10 friends helping you, that's 15 or 16 10k's at a time.
You don't think that the casinos are going to be compiling pictures of everyone cashing in 5k or more in chips for the next couple of years? Their own internal investigation will find the guy. All they need to find is the people cashing in multiple quantities of chips. The smaller the amount at a time, the more times you're going to have to cash in. The larger amount at a time, the larger the red flag. "Hey, look at these pictures. This guy cashed in between $5k and $15k worth of chips 18 times. The chips were all from the Bellagio. We have no record of him playing there."
He may succeed in cashing in a few thousand, but as soon as he repeats it 2 or 3, or maybe it'll take 5 times, but they'll figure it out.