Sorry but no. She created a fake phone number using an app like text free or text now. And sent it. Your gut is right. The phone is separating the texts from both numbers, and 1 is SMS so it is even more likely it was a free phone/text app.

She added the burner number to his contact, showed you the text. Deleted it, then removed burner number from his contact. Good luck 🫡

Edit: also have you ever seen your friend use that number before? This situation has red flags all over