Well, there was so much snow blowing around that Jack Frost didn't see that he had the wrong hat.
8 seconds sound clip from the Frosty's Winter Wonderland movie soundboard.
You can hear this line at 00:07:01.970 in the Blu-ray version of the movie.
Quote context
[...]
- You're right, Frosty. You can't count.
- If I could just aim my north wind at that magic hat.
- Got it! Frosty's magic silk hat! It's mine! It's mine!
- Well, there was so much snow blowing around that Jack Frost didn't see that he had the wrong hat.
- Now those children won't have any winter friends.
- And wearing a horse's hat, he took off for other faraway wintry places.
- Suppertime, Frosty. Mom wants us home.
- Yep.
[...]