Please calm your catastrophizing,,( understandable)
Use this experience to better yourself ,as you say you want to get your head down and study , brilliant.
Trust me you need to back away from "freinds" that carry on like this.
In the big scheme of things you only stole something insignificant but this puts you in a situation of dealing with police and courts .yes its wrong but the behaviour of such acts can escalate and leave that to your "friends" if they want that in there future.
Nothing serious will come of this,learn the lesson ,,distance from these "friends " would be the best outcome .
Take care .