No. To be charged for "aiding and abetting" or as an "accessory" to the theft, you need to have both:
known about the crime and
acted to help carry the crime.
Someone who unknowingly helps carry out a crime cannot be charged with aiding or abetting.
Obviously, since you didn't know beforehand that your friend was going to steal from the store, you can't be charged for that. Whether you can be charged with "aiding or abetting" after-the-fact depends on when you found out, and what you did with that knowledge. Suppose you lied to the police to give Bob an alibi, or helped him sell the loot. Since in those instances you knowingly helped him carry out his crime, you could be charged.
