If you had consistent gravity then the airlock bubbling is probably not restarted fermentation but rather CO2 coming out of solution due to adding nucleation sites --
"Pellet hops also have to be weighed, but are probably the easiest type of hops to pour through a carboy neck. They are also easy to put into a bag, but only a very fine bag will contain the powder when they dissolve.
On the other hand, pellets can cause a sudden eruption of foam that will have you scrambling for a towel and wondering what sort of alien being has taken over your beer. This is because as the pellets break apart (almost immediately) they provide thousands of nucleation sites for the CO2 in the beer to attach itself and come out of solution. Be careful and go slowly when adding pellet hops to any nearly full container.