There isn't any way to tell if it has, it would just be like normal use.
Best thing to do is keep an eye out for any transactions that you never made, like App purchases or song downloads. Even better, is to make sure it doesn't get hacked in the first place! Always have a secure password on your online accounts:
Make sure your passwords all have:
> over 8 characters
> a combination of letters/capital letters and numbers
> special characters like * ( ) - < > ! ^ $
> doesn't contain your name, date of birth or other easily guessable word.
Also, don't use the same password twice (like for your Apple account and email), it's not secure: if someone guesses your email password, they can get access to your Apple account. Ideally, have four or five passwords that you can rotate regularly.
If you want to test your password security, try out this website: http://howsecureismypassword.net
Hope this helps you out!
(NOTE: you will be leaving Apple's website by clicking the above link, do so at your own risk)