Is it possible to fly standby and use the 72 hour transit visa?

I'm an airline employee who will be travelling on standby with a booking number and ticket for my continued flight to Hong Kong. I just won't have a seat selection but can provide a reservation and ticket if asked. I'll be staying in Beijing for only two days.

Will they accept my ticket and booking? And if not, is it possible to book a fully confirmed refundable ticket onwards on a different flight departing within the 72hrs and show that to customs uypon entry. Then use the standby ticket to leave? Will they know, and would they get upset even if it's all within the 72 hour limit?