Citibank did the same thing to me a few months ago, and it seems to have had no impact on my credit score, which was in the 800s and has increased by 2 un-dramatic points since.
Right before my Citi card was closed I had just opened another credit card (to collect the bonus), and I was concerned that maybe one thing had something to do with the other, but folks here assured me that timing was just a coincidence. Opening that other card did mean that my total credit limits stayed right about the same, and my overall credit utilization is less than 1%, and my credit history is older than it sounds like yours might be, so any of those things might make our experiences a little different.