Your chances of getting a female is >50%. The reason that I say this is that normally you would have a 50/50 chance of getting a female, but you mentioned that it was really good marijuana, leading me to believe that it could have been home grown. You also mentioned that you found a seed, not seeds, which furthers my assumption that it was probably home grown marijuana. If it was indeed home grown marijuana, the seed was probably produced when a female plant was pollinated by another female plant (female plants produce male flowers when under stress), producing feminized seed.

Your chance of having the plant produce without male/female interaction is almost 100%, assuming that you aren't currently growing any male plants in the house and that you don't live in the middle of field full of hemp.

What are the odds that you are going to end up with smokable bud? I'll give you a 1% chance, but only because I am nice.