Verifying warranty status

I have a 6th gen (current) iPod classic. It's always attached to my car, except for when I need to update it with new music.

Recently, it's been freezing up a lot, so I figure something is wrong with it.

Except I can't figure out if there is still warranty on it; I don't remember when I bought it and the Apple warranty checker says I need to verify the purchase date. And I don't know where the receipt it.

Should I go to the Apple Store anyways or should I resolve this warranty issue first?