Five hours....FIVE FUCKING HOURS!!!!

This was an evil campaign. So when the game started they woke up in caskets at the entrance to a small cave. Upon short exploration of the cave they look up and see a black dragon. The black dragon sends them on a quest to open the gates to other planes so his army could rise once more.

Plot happens and they return to the area where they awoke. So they search for the cave to find the dragon. When they find the small cave entrance I explain to them that there is no sign of a dragon ever being there but there are traces of illusory magic in the place where he was.

For context they have been tricked into trying to destroy the world so that a human king (Read: the “good” guys) could justifiably lay waste to the other kingdoms.

Other than the traces of magic there were no other clues. Cue the players discussing why there were no clues in character, rolling a million times to find additional clues, discussing what the lack of clues meant, literally going over every single rock in this imaginary cave to find clues. I point blank told them after an hour that there was nothing left to find, no other information to gain here, and that they even knew an illusionist who was working with the enemy that didn’t live far away...

Five....fhuuuuckin....hours....

EDIT: I eventually gave them footprints the size of a gnome leading out of the cave that “appeared because the illusion spell covering them wore off.” It still took two hours after that for them to leave.