Lionel wrote:

No and I am by no means an expert on these things but I will have a
guess. The heavier line pulls harder due to centrifugal force and
this is slowly unreeling it, luckily at a useable rate. In any case
bless the day that you have serendipity and not sod's law at your
house.

I agree with David, the same happened to me.

But as an aside, centrifugal force is fictitious.

http://en.wikipedia.org/wiki/Centrifugal_force

If I had said the line was unreeling due the greater tension from using
heavier line brought about by constraining rotating objects having a
tendency to continue their motion in a straight line in accordance with
Newton's laws of motion, would it have helped any more in the given
situation? So I said centrifugal force and everybody knew what I meant.

David