Solved by David Grenier

solution: painfully easy

Assuming complete honesty on the part of the flipper, wouldn't the solution be 33%?

There are four possible scenarios:

HH
TH
HT
TT

Obviously the TT possibility can be discounted because it does not result in one of the two being heads.

This lees us with three possibilities, only one of which has the other coin also being heads. 

Therefore one third.

I think.

I usually get these wrong.