I would not be discouraged by this. There is dissolved CO2 in your beer after fermentation that will come out when given the chance. Racking is one way it comes out, and putting hops in is another. The hops provide all kinds of places for the bubbles to form. If the yeast wasn't quite finished, then the hops provide a nice blanket for foam to form. Don't worry. If you took a gravity reading at racking, take another one in a week or two and see if there is any real activity going on.
If you are a beginner, I wouldn't get too caught up in dry hopping at this point. You should be able to make a fine beer without it. I think at the beginning, it's important to get your processes down and make a clean beer without other things possibly mucking things up. Once you can make a couple of good, clean IPA's in a row, then try an extra technique like dry hopping.