Yes, any collector can do an 'asset assessment', there are tons of public sources they can access that will show if you have any assets that give them some handle on your financial situation.
As for changing collection agencies, this happens ALL the time and they do NOT have to notify you of the change. You'll just get a new letter from the new CA trying to collect. I'm already up to the THIRD CA on one account, they try for just so long then they give up and send it somewhere else. Its not worth it to them to keep trying so they pass it on.
What is the 'extra' $1000 you're saying they tacked on ? They are typically allowed to add interest if it was in your original card agreement.