Thank you message to boyfriend HELP!?

So my boyfriend are hitting one month in a few days and the other day he went to hershey park and got me this heart necklace and is so pretty! I said thank you and gave him a hug and kiss on the cheek, but he gave it to me at school and I had to go to my bus before saying anything else. He has his phone taken away right now so the only way I can talk to him is via facebook. I want to send him a sweet little thank you message but don't have any idea what to say! HELP!!!!!