Glad he is finally out of the house, you both must be so relieved.
Out of curiosity, is he deaf?
White cats with heterochromia can be deaf due to the W gene (white) and more likely to be so, if 1 or more blue eye is present.
I learnt about this when I dropped a plate next to my white cat with blue and green eyes and he didn't even flinch, I've also had a white cat that hear just fine with green eyes.
Could be why he couldn't hear you calling from the open window.
Hope he has learnt his lesson, but I doubt he will have, the age old saying.. Curiosity... The cat.