Oh boy do I have to drive out and its most simplest form for you? No duh! You put a little plastic plug in there that fits just nice and snug like the slip yoke. Or a spare slip yoke. people don't generally wait things they're pulling to the rear.
DARTFREAK..... here are your two choices with a dolly:
crawl under and removed drive shaft, wire a spare yoke in the tranny, then when you get to the drag way, crawl under and remove tied in spare yoke, and re-install drive shaft.