Because I've had folks seem surprised when I tell them you should never thank someone for a gifted plant, I'm passing on the lore here.
You should always just say something like "I hope I can care for this until it blooms" or "what a gorgeous cutting/bloom/plant youve shared with me!"
Thanking them for the plant ensures it will wither. Because sharing a plant, especially a cutting or bulb, is an act of community. They aren't giving it to you for praise. They're giving it to you for connection.