"Drone" disappeared after engaging 4 wheel

I started noticing a droning noise over the last week, almost like a wheel bearing was going bad. Then on Friday, we got hammered with snow, so I went into 4 wheel mode until I got to the highway, then drove 400 kms. Now, the noise seems to be gone. Is it I was negligent in periodically going into 4 wheel drive to keep everything lubricated (I think I was doing it monthly, but may it'd been a couple of weeks longer). It also sat for two weeks while I was on vacation in Florida, but I can't imagine that caused any issues. Or just chalk it up to, "Who knows? It's gone now, so forget about it"? I'm more curious than anything. Seems strange to me.

 

Front diff bearing possibly

 

Could have lubed stuff like you said, and spun things around so that maybe what was droning, is now in a better position and isn't making said noise now...??