I've had a payment sit unclaimed twice. The first time it was a DS FSOT transaction and I typed the seller email addy wrong. The second time, I bought from an online store through their checkout system and it sat unclaimed for a few days but then went though.
It's weird that it would be unclaimed via HC. That should just automatically go into the seller's account. Is it a new seller? Could they have possibly entered their email addy incorrectly? Could there be a freeze on their PP account?