Do you have the ability to offer him a different perspective? Along the lines of what Allberg has mentioned, if you guys are able to go outside during the day, there’s a plethora of things you can do. Not to mention it’s a great bonding opportunity between you and him.
Social interaction is rather important to the majority of us. Spanning most age ranges. Granted the situation might be a bit different, and therefor new, his reaction is quite normal.
I’m not a mom, but I don’t necessarily have to be to at least offer some help, or encouragement, or whatever third thing this would be called. Whenever you do talk to him, try to focus on future events. I call it “hopeful planning”, but essentially it’s speaking in terms of remaining as positive and hopeful towards better future instances than the current one.
Try to understand the “how” part of what he’s feeling. His friends are/were providing a positive stimulus. And don’t get me wrong, I totally DONT view friendship as some sort of scientific/biological process that’s need to be broken down to mere bits and pieces, but there is an ebb and flow, of some sort, to it. This might sound weird, but try to simulate those interactions with him. What did he and his friends talk about? What did they like to do? What didnt they like to do? Ask him that. Then go about doing those things Or at least compensate the best you know how by trying to do those things, and/or talking about those things.
There’s a word that I can’t think of right now, but it’s best described as association. A lot of the times we as individuals, regardless of age, like things not because of the things being the things in and of themselves, but how doing the said things make us feel. Your son enjoyed the good times, the laughs, the connections, etc. that were specific to him being around and with his friends. I do understand the dynamic is different for each individual, but if there’s a way to bring about those same feelings, the methods of doing so don’t particularly matter. At least in my opinion.
So when I speak of the “hopeful planning”, try to use words that imply that he’ll see his friends again, and this is merely temporary. Positive reinforcement, if you will.
And a few folks on here and mentioned some really great ideas as well. This is just what I have to offer. Hopefully it wasn’t confusing.