Jesse contacted him back

After taking a long needed shower, Sam grabbed his towel and wrapped it around himself before heading out of the steaming bathroom. Right when he was about to head to his room, a voice called out from the bunker's library "Sam Winchester?". Along with hearing the voice, he also noticed the lights flickering. Was that Jesse? Probably, Jesse was around eleven when they met, the voice he's hearing now didn't belong to that of an eleven years old, granted it's been ten years so the guy was at least twenty-one years old by now.

Sam grabbed an iron rod in case it was a ghost and headed to the library where he had tried summoning Jesse before. There, he sees the crystal ball again, this time glowing by itself, and floating too. It was glowing various of colors and filled with smoke like last time, "Sam!" it was clearly coming from that crystal ball.

"Jesse." he spoke, he was sure it was him. He got to the floating ball but kept his safe distance.

"Come here!"

He reached for the floating crystal ball. What happened next was out of his control. The floating orb glowed brighter as soon as Jesse said that, and Sam vanished from the library, still in towel.