The rule (for me) seems clear: First, loose a Rune point (not POW). It is ambiguous if an already spent RP can be sacrified or not. Then roll the dice (1D10 or 1D100), spend a number of unspent RP equal to the dice result. If the number of available unspent RP is lower than the dice result, loose a number of POW equal to the dice result minus the number of available unspent RP. If the power is brought to 0, the character dies. If the result of the dice is greater than the number of available RP + POW, the DI failed because the god did not answer.
The 1st RP is definitively lost. The other are then spent, and have to be regained as if spells had been cast with them. Lost POW points have to be regain by POW gain rolls as usual.