Had the cabin crew already shown the safety video and walked thru the aircraft chacking all the pax.?
If it happens again, maybe an idea would be to stay standing until you have the seatbelt. I bet they wouldn't have forgotten you then.
Not very good unfortunately.. I and other crew, I have noticed, tend to have a couple handy in the cabin for whilst pax are boarding, so they can have them straightaway. We need to make sure the pax knows how to use them. It can be tricky to go to the stowage whilst pax are boarding, if the stowage is at the other end of the cabin, and you have to keep door cover. Makes it alot easier if we have them to hand..