No way did the 3 hours jet lag have that effect, especially not going west to east. I've had up to 12 hours jet lags and 3 hours is nothing. It might affect you a bit for one day, but that's it.
I did two trips to Europe in the past 6 weeks (still there in fact) and both times I had between 5 and 7 hours of jet lags and both times I had zero problem training the next day.
However dehydration might have been a problem. The more time you spend in the air, the more dehydrated you become and that can greatly affect your strength and it can take 1-2 days to get back to normal.
Now what is more likely happening is that you lost your neural edge by not training. Your whole system is based on making the nervous system super effective. By definition the GtG approach actually cause only a small amount of structural changes (muscle growth) and it happens VERY gradually. The progress is mostly due to neural adaptations, which occur VERY rapidly but are also lost very rapidly; whereas structural adaptations are maintained for much longer.
It was a big mistake to start a new cycle with more weight. When using a neural-dominant approach like GtG, a week without lifting basically sets you back 1 weeks. So you have to start 1 week "earlier" in your program, maybe even two. Starting a new block, with lowered neural adaptations yet using more weight is a bad idea.