I agree with Karen. As a boss myself, I think communication is very important. I make sure to let my staff know what I expect and when. In regards to "small talk" and socializing at work, I feel lilke I'm paid to do a job and so is my staff. I don't mind small talk if the necessary work is getting done. But people standing around chitchatting isn't what they are being paid for. I agree it should be a pleasant work environment and I would say that if people don't greet you it could well be that they are immersed in their work. I make a point of saying hello to everyone everyday and find that it makes people aware when I pass by and they always greet me. Sometimes before I do!
I don't think it helps to worry about it when there' nothing you can do about it till your boss returns. Talk to him then to clear the air.