One comet, billions to go
While I have my doubts we will find actual life on a comet, one sample is not enough. And did you note how the Universe has a funny way of totally ignoring our pre-conceived notions and theories whenever it feels like it?
Just as most scientists used to think the ocean floors were nearly devoid of life - until they found all those incredible life forms around those hydrothermal vents in 1977 - comets and other celestial bodies we might never have considered before as life havens may surprise us.