@pax1sw
Oh yeah, sorry, I forgot he was a celebrity. He's in my game but I don't see him around much and never played that household. Celebrities are different than non-celebrity sims. You have to get the celebrity to acknowledge you before you get the regular social menu options. So, you have to keep hammering the attempt introduction option until they wave and make that sound they do when they acknowledge you, then you get a few more options and finally get to the regular socials. With some celebrities it can be really hard to do. A lot of the time, even if you cheat the friendship and romance bars, it is still hard to get by the attempt introduction, especially since that option has a cooldown and you can't spam it. So, all I can tell you is to keep trying.
Again, if you are willing to use a cheat, with testingcheats on and shift click on Thorne, you can reset him when he tries to walk away to keep him there to talk to but sometimes that doesn't work. They will still walk away. But if it does work, it will let you keep trying to introduce your sim to him. Sooner or later, he will acknowledge you if you keep at it but sometimes it can be really hard to get there.
If you have Lovestruck, there might be another way. I have not tried it myself, but I've read about it in a few places. One of the last updates, according to what I read, gives the option to ask a ghost on a date via the phone. But in your case with a celebrity, it may not work, because a lot of the time, celebrities won't show up to choose as a date when you haven't met them. As I said, I have not tried it and really don't know how it works. But you might give that a try if you can.
Hope this helps.