Yes, it's a common word. Mostly seen in sports reports or whale watching articles.

I understand a fluke to mean an unusual occurrence, not likely to recur.

I've also been hearing flukey a lot lately used as an adjective.

In this context, this sentence could be rephrased as:

"That dream came true...and it wasn't an unlikely chance occurrence either."

A fluke used as a noun in this context is defined as an unlikely chance occurrence, especially a surprising piece of luck. Put another way, it is a lucky or improbable occurrence, with the implication that the occurrence could not be repeated. For example:

"The golfer's hole-in-one was just a fluke."

Hope that helps.

Thanks guys!

Will