I'd say no.
Think of it this way... You buy a box. It is locked. Something is in the box. But you must purchase a key separately from the original purchase to open said box. You use a hairpin instead and open the box. That is not stealing. You had the contents of the box already. When you purchased the box, it contained other items, and despite the request for a second transaction, you still have in your possession the items from the first purchase. I'd wager the key is a convenience item, not a mandatory secondary transaction.
Therefore, to open the box and retrieve the items included in your original purchase through cleaver means is NOT stealing.
However, if you SIGNED an agreement to never open the box unless you purchased the key... that'd be another story. Probably not so much as stealing as a breach of contract though.
Think of it this way... You buy a box. It is locked. Something is in the box. But you must purchase a key separately from the original purchase to open said box. You use a hairpin instead and open the box. That is not stealing. You had the contents of the box already. When you purchased the box, it contained other items, and despite the request for a second transaction, you still have in your possession the items from the first purchase. I'd wager the key is a convenience item, not a mandatory secondary transaction.
Therefore, to open the box and retrieve the items included in your original purchase through cleaver means is NOT stealing.
However, if you SIGNED an agreement to never open the box unless you purchased the key... that'd be another story. Probably not so much as stealing as a breach of contract though.