What is the deal with this cat?

There is this adorable young cat outside my job who would always want to sit on my lap. With weather being bad, my friend offered to foster him with the hopes of keeping him. I got him in the carrier and he was fine, a little fidgety but no crying. My friend said once they were home he instantly cuddled and kneaded her but was breathing heavy due to the car ride. The next morning, after he slept in her room but cried and climbed and pawed at the window most of the night, she had a bad reaction to him so I had to bring him back. He did not eat or use the bathroom at her house and on the car ride back, he was crying and panting incessantly. As soon as I let him out back at my job, he knew where he was and drank some water. He also wasn t mad at me and wasn t too skittish. It s rainy and I feel bad but is he not ready for an indoor home? He s also unneutured. He s loving and sweet but I can t tell if he is ready for a home or is he more comfortable outside? Can anyone help?? I hope he s not traumatized