In most cases, messages sent to a temporarily absent number will usually be placed in the Carrier's Retry Scheme and will be delivered once the number becomes available, or will expire after 24 or 48 hours (even in some cases up to 72 hours) depending on the destination.
If this fails the carriers will either return a FAILED status with Error 2 - Absent Subscriber Temporary, or an EXPIRED status to you. Once this is returned, no more retries will be performed by either the carrier or Nexmo.
One example of a common retry scheme for Absent Subscriber Temporary Numbers is as follows:
SMS validity period = 48h
1. retry – after 1 min
2. retry – after 6 min
3. retry – after 8h 6 min
4. retry – after 24h 6 min
5. retry – after 48h ( no retry ------> SMS validity expired)