That could be possible if you have a deep sand bed, or if you stirred up a lot of crud. Usually you will want to stay away from siphoning the sand bed, especially if it's deeper than a few inches. If this is the case I wouldn't say that the "chemistry" has restarted, you merely disturbed and or kicked up nutrients into the water column that are now breaking down, resulting in your high NO3.
Now if enough nutrients were kicked up to cause a spike in ammonia, then you could say the tank is re-cycling or "restarting". However since you haven't reported the fish being stressed, or any losses, I doubt the tank is cycling very severely, if at all.