Incorrect Order Status On New Order

Processed 20000+ orders so far and never seen this but last night an order was placed which came through as 'Awaiting Stock' rather than the usual Payment Received or Failed, Telephone Payment.

There were 6 of the product in stock and the customer ordered 5 (which decreased to 1 correctly)

The product is set to sign up for notification when out of stock (my first thought was that it was set to pre-order by mistake but not the case).

Looking at the order and product i can see no reason for this which is always a worry, anyone got any ideas?

CScart v3