That is on the OP (as has been said).
Eh, well, not 100%, in this case.
You don't know what you don't know.
Now obviously, I didn't hear the conversation myself, but If I signed up for my first NJ dive, and was told by the person running the charter "... no problem you should be fine with teaming up with a buddy when you get there" (as the OP stated), then I put the some of the blame on whoever told them that.
At the very least, it would have been good to have a conversation sometime before the new diver showed up on the boat. Our club does try to do that for our charters, and we have a mailing list where everyone can email the other divers to try to work this out ahead of time.