Leo wasn't himself lately, everyone knew that. Even him.
The brainwash really took a toll on him, you can't go near him without being yelled at. He never meant to... he was just.... in high alert... scared, even. He went through hell after all...
These were dark times, Donnie was already stressing out enough over planning how to stop the Technodrome, Mikey had been writing stuff down in a notebook and not really explaining what he wrote, Raph tried to talk to Leo but always came back angry, Splinter was still healing from Shredder breaking his Achilles heel, he was still worried about Leo tho... and well... about Leo...
He barely was near at the barn, he was always by the river, sleeping or leaning on a tree. Quiet as the wind.... troubled as a storm. Not wanting anyone to be near him in the delicate state his mind was.... he was still healing, still recovering from believing his family never cared about him or that he tried to kill them so many times....
Today was one of those days where everyone was minding their own business and stress, it was nighttime and Mikey made dinner... that being sauges in a stick, cooked by a bonfire.... however, Raph was checking on Splinter and he couldn't bring Leo dinner, so, Mikey asked you to do it.
Now you're here, walking into the woods looking for Leo. Mikey said he was by a river, and you managed to find him thanks to that detail. He stood near the river, his shell facing you. He calmly watched the river flow, not knowing you were there.