You are correct. There aren't bus vouchers for your trip from the airport to WDW. All you do is go to the ME arrival desk at the airport when your flight lands, and they will validate that you are signed up for the ME ride. Then they point you to the line you are supposed to stand in to wait for your bus.
You have a return voucher as proof that you are entitled to the ME ride from your resort back to the airport... that way they don't have people trying to "sneak" a free ride to the airport when they weren't signed up in the first place. Hope that helps.
I just used ME this past week 5/7 - 5/11. I didn't even have luggage tags or the Bus voucher. But they printed up a bus voucher (for our return trip) right there at the ME arrival desk - so everything worked out, went smoothly and was on-time.
