Hello dexnutslols.
Thank you for using Apple Support Communities. Try removing that specific contact out of the group text by following these steps here: Add and remove people in group text messages on your iPhone, iPad, or iPod touch - Apple Support
How to remove someone from a group text message:
1.) Tap the group message that has the contact you want to remove.
2.) Tap the group icons at the top of the thread.
3.) Tap the gray arrow icon to the right of the contacts, then swipe left over the name of the person you want to remove.
4.) Tap Remove, then tap Done.
Once removed, you can attempt to re-add that specific contact that was missing by following these steps here:
Add and use contact information on iPhone - Apple Support
1.) Open Contacts app
2.) Select the "+" icon on the top right corner of the screen
3.) Type in details and select "Done"
After you've added your contact back, test to see if you're able to message them directly. We hope this information is helpful. Cheers.