As I said, I didn't look this one up but mutual funds frequently do go through mergers and consolidations that are tax free. I'm sure you got some information about before the change happened and I'm sure that information told you whether the transaction would be taxable or tax free.
That said, brokers prepare 1099-B's when they are necessary don't prepare them when they are not, so I'll bet you a dollar and give you 5 to 1 that this was a tax free merger.
