Hello Douglas,
When it comes to tip recipients who do not currently own a hive account, they get right away notified in twitter and information on how to get a new hive account is included.
EDIT: Currently there is no such a reference on how to get a HIVE account because of the Twitter max 300 char limitation.
In the meantime, funds stay in the central pool "hivetips.pool" until attestation process is fulfilled.
We will write Q&A on this topic anyways, thanks for pointing this out.
Cheers
Daniel