Shadowheart's artifact immediately hops onto you if she is dismissed from the party and cannot be given back afterwards, so even if she is not in the party the artefact is always with you.
As for the dead boar, it's just a tiny bit of foreshadowing. The player can only find out about Astarion being what he is after sleeping in the camp.
I know that part about Astarion. Was just curious if you don't see the boar or anything else, would he just try to bite you one night.
