I'd bet the ticket slipped through the cracks--it might have been pulled by an agent near the end of their shift who thought "I'll respond first thing tomorrow" and was let go the next day, or the ticketing system glitched and improperly took it out of the queue, or a tier 1 agent didn't follow proper escalation procedures and reassigned it to someone who never bothers to check their ticketing queue.

I'd suggest submitting a fresh ticket along the lines of "Following up re: ticket 29XXXXX" and copy-pasting the original message into the new ticket.

Source: work for a different company's support team that also uses a public-facing ticketing system