Heh... dead easy that one, peops, but you're still going to get it in the neck for messing up.
Tell the captain the truth and then ask him/her for their decision. Slopy shoulders. Frankly, if there was no standby cover, the chances of a ramp check are so small, I think it would not be a problem to despatch. If you do get pulled up, you genuinely own a licence and a passport (not needed if you're not disembarking the aircraft), so it's just a case of paperwork and hassle, depending on your destination. Won't make you popular, but it's a business.
If you're going to Zurich or somewhere similar.. to hell with it.. go. If you're going to Jeddah or Florida.. ermm.. well, delay the flight, go home, get your stuff and take it in the neck.
The truth always wins, and the captain makes the final decisions regarding the crew. Remember that, and you can't go wrong
