Good on you for posting Michael, I think you already know that its impossible for nicotine addicts like us to have "just one" or smoke "just while......". So now that we have that answered, there's something about the three's. Three days, three weeks, three months that make the craves suddenly come on strong. Don't quite know the science behind it but it happens to A LOT of us.
That being said, just that you posted tells me you REALLY don't want to cave and that alone should give you the confidence you need to get past it. It's only temporary and it will pass.
One trick I used when I was having a bad crave day was using my JAC (jillars air cigarette), I just pretended I was holding an actual cigarette in my fingers and then went through the motions of "smoking" it. It worked REALLY well at tricking my mind into thinking it was getting the real thing.
You're doing great and I'm so glad you cancelled your trip to Vegas, it's a horrible time with this virus to be in a casino!