Heaven:
Cas leaned back in his chair and sighed with relief. At last the processing was complete. Ever since the virus struck, he and the rest of heaven had been in 'all hands on deck' mode. Over seven billion souls to be sent to their afterlife sure took it out of a celestial being.
It didn't help that the newly dead were a grouchy bunch. You'd think that they'd have been relieved at getting into paradise. But no, the line at the sandbox turned into a stampede worse than Black Friday at Walmart. Aziraphale, the angel on gate duty, had been trampled. His wings hadn't healed yet, and he kept giving Cas dirty looks.
Even worse, this apocalypse hadn't just affected human souls. Every shifter, vampire, werewolf, wendigo, ghoul, skin walker and miscellaneous monster had been felled by the virus. The reapers on purgatory duty had left a post-it note on Cas's chair saying "We can't take it any more" and decamped to Pluto, leaving a motley crew of cherubim and cupids to handle the crowd.
As far as Cas could tell, the only being left on earth was Crowley. He took a moment to savor the thought of Crowley presiding over an empty hell before ordering Aziraphale to locate the Winchesters, then settled in for some serious drinking.
Several hours later Cas's boozing was interrupted by a knock on his office door. Quickly shoving the bottle of vodka into a drawer, he hiccupped and said, "Come in".
Aziraphale entered the office. Waving the alcohol fumes away, he said, "Uh, sir, there's a small problem with the Winchesters."
"Of course there is," Cas said. "What is it now? Dean won't leave his heaven? Tell him I want to see him now. He can get back to his pie and strippers later."
Aziraphale looked embarrassed. "It's not that. Winchester land is empty. They aren't here."
"What do you mean, they're not here?" Cas said. "They have to be here."
"They haven't shown up," Aziraphale said. "We've checked everywhere. Sam and Dean Winchester aren't in their heaven".
A thought struck Cas. Knowing the Winchester habit of breaking the rules, it was entirely possible that they'd ended up somewhere else. "All right, then," Cas said. "Check out the heavens of all of their known associates."
"Yes sir," Aziraphale said. He returned hours later looking freaked out.
"What did you find?" Cas said.
"Um, I did find a Sam Winchester in one of the heavens," he said. "But I don't think it's the one you want. "
Cas frowned at him. "What do you mean? he said.
Aziraphale blushed. "It's the private heaven of a Becky Rosen and it's pretty . . . graphic," he said.
"Don't be ridiculous. I'm an Angel of the Lord. I've seen everything in my time," Cas said. "I will visit this heaven immediately."
"Trust me, you really don't want to go in there," Aziraphale said.
Cas ignored him. Arriving at Becky's paradise, he opened the door, gasped in shock, and promptly slammed it shut.
"The horror, the horror," he moaned as he headed back to his office. He pulled out a bottle of whiskey, knocked back a slug, and said to Aziraphale, "I know he's not really Sam, but that poor, poor, bastard."
Many bottles of booze later, Cas sat in his office nursing the mother of all hangovers. Well isn't this just peachy? he thought. If Sam and Dean aren't here in heaven, Crowley must have gotten them. Great, another rescue mission. How many times do I have to pull those clowns out of hell?